Fair Value Measurements - Schedule of Cash and Available-for-sale Debt Securities' Amortized Cost, Unrealized Gains (Losses) and Fair Value by Significant Investment Category (Details) - USD ($)	Dec. 31, 2025	Dec. 31, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	$ 943,536,000	$ 147,691,000
Amortized Cost	4,105,023,000	1,859,871,000
Unrealized Gain	7,185,000	3,583,000
Unrealized (Loss)	(136,000)	(1,012,000)
Fair Value	4,112,072,000	1,862,442,000
Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	3,448,903,000	1,705,657,000
Unrealized Gain	7,185,000	3,583,000
Unrealized (Loss)	(136,000)	(1,012,000)
Fair Value	3,455,952,000	1,708,228,000
Cash & Cash Equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	943,536,000	147,691,000
Cash & Cash Equivalents \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	298,237,000	0
Available-for-sale Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	3,157,715,000	1,708,228,000
Available-for-sale Securities \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	3,157,715,000	1,708,228,000
Restricted Cash (Current and Non-Current)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value on a recurring basis	10,821,000	6,523,000
Restricted Cash (Current and Non-Current) \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0	0
Time Deposits \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	100,000,000
Unrealized Gain	0
Unrealized (Loss)	0
Fair Value	100,000,000
Time Deposits \| Cash & Cash Equivalents \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	100,000,000
Time Deposits \| Available-for-sale Securities \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0
Time Deposits \| Restricted Cash (Current and Non-Current) \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0
Corporate bonds \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	1,271,232,000	466,769,000
Unrealized Gain	3,304,000	1,125,000
Unrealized (Loss)	(54,000)	(316,000)
Fair Value	1,274,482,000	467,578,000
Corporate bonds \| Cash & Cash Equivalents \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0	0
Corporate bonds \| Available-for-sale Securities \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	1,274,482,000	467,578,000
Corporate bonds \| Restricted Cash (Current and Non-Current) \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0	0
U.S. treasury securities \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	1,760,179,000	1,120,478,000
Unrealized Gain	3,859,000	2,403,000
Unrealized (Loss)	(4,000)	(677,000)
Fair Value	1,764,034,000	1,122,204,000
U.S. treasury securities \| Cash & Cash Equivalents \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	59,768,000	0
U.S. treasury securities \| Available-for-sale Securities \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	1,704,266,000	1,122,204,000
U.S. treasury securities \| Restricted Cash (Current and Non-Current) \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0	0
U.S. government agency securities \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	146,986,000	69,872,000
Unrealized Gain	22,000	55,000
Unrealized (Loss)	(78,000)	(19,000)
Fair Value	146,930,000	69,908,000
U.S. government agency securities \| Cash & Cash Equivalents \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0	0
U.S. government agency securities \| Available-for-sale Securities \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	146,930,000	69,908,000
U.S. government agency securities \| Restricted Cash (Current and Non-Current) \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0	0
Commercial paper \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	170,506,000	48,538,000
Unrealized Gain	0	0
Unrealized (Loss)	0	0
Fair Value	170,506,000	48,538,000
Commercial paper \| Cash & Cash Equivalents \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	138,469,000	0
Commercial paper \| Available-for-sale Securities \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	32,037,000	48,538,000
Commercial paper \| Restricted Cash (Current and Non-Current) \| Level II
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0	0
Cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	68,297,000	51,410,000
Unrealized Gain	0	0
Unrealized (Loss)	0	0
Fair Value	68,297,000	51,410,000
Cash \| Cash & Cash Equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	57,476,000	44,887,000
Cash \| Available-for-sale Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0	0
Cash \| Restricted Cash (Current and Non-Current)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	10,821,000	6,523,000
Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unrealized Gain	0	0
Unrealized (Loss)	0	0
Money market funds \| Level I
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	587,823,000	102,804,000
Unrealized Gain	0	0
Unrealized (Loss)	0	0
Fair Value	587,823,000	102,804,000
Money market funds \| Cash & Cash Equivalents \| Level I
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	587,823,000	102,804,000
Money market funds \| Available-for-sale Securities \| Level I
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0	0
Money market funds \| Restricted Cash (Current and Non-Current) \| Level I
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	$ 0	$ 0

Cloudflare, Inc. 10-K