Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Income Tax Contingency [Line Items]
Income (loss) from continuing operations before income taxes		$ 83,361	$ 44,130	$ 41,418
Book loss from foreign operations		9,000
Current taxes [Abstract]
Federal		(489)	(209)	34
State and local		(5,490)	(230)	(170)
Foreign		(1,523)	(1,070)	(856)
Deferred taxes, net [Abstract]
Federal		(10,509)	(26,693)	(8,858)
State and local		(2,908)	(2,099)	(2,478)
Foreign		2,698	226	150
Income tax provision		(18,221)	(30,075)	(12,178)
Reconciliation of income tax (provision) benefit [Abstract]
Income tax provision at statutory federal tax rate		(17,506)	(15,446)	(14,490)
State and local income taxes, net of the federal benefit		(6,635)	(1,514)	(1,720)
Non-deductible expenses		(14,373)	(26,196)	(20,715)
Foreign jurisdictions rate differential		250	374	216
Recognition of excess tax benefit		8,972	18,415	20,966
Research credit, federal benefit		7,045	4,688	3,727
Enactment of Tax Cuts and Jobs Act		0	(9,750)	0
IRS audit settlement		4,123	0	0
Other, net		(97)	(646)	(162)
Income tax provision		(18,221)	(30,075)	$ (12,178)
Tax Cuts And Jobs Act Of 2017, deferred tax asset reduction	$ 8,800
Deferred tax assets [Abstract]
Net operating losses	2,504	2,504	34,771
Tax credit carryforwards	1,639	1,639	1,807
Research credit	35,014	35,014	27,559
Deferred revenue	259	259	497
Accruals not currently deductible	4,158	4,158	1,137
Allowance for doubtful accounts	454	454	238
Charitable contributions	1,868	1,868	1,729
Stock-based compensation	13,646	13,646	9,851
Deferred rent adjustment	3,239	3,239	2,128
Foreign deferred tax assets	1,673	1,673	0
Gross deferred tax assets	64,454	64,454	79,717
Less: valuation allowance	(1,673)	(1,673)	0
Net deferred tax assets	62,781	62,781	79,717
Deferred tax liabilities [Abstract]
Property and equipment	(35,843)	(35,843)	(47,022)
Deferred commissions	(12,306)	(12,306)	0
Foreign, primarily acquired intangible assets, net	(25,105)	(25,105)	(250)
Gross deferred tax liabilities	(73,254)	(73,254)	(47,272)
Deferred tax liabilities, net	(10,473)	$ (10,473)			$ (421)
Deferred tax assets, net			$ 32,445
Income Statement
Reconciliation of income tax (provision) benefit [Abstract]
Tax Cuts And Jobs Act Of 2017, deferred tax asset reduction	8,700
Other Comprehensive Income (Loss)
Reconciliation of income tax (provision) benefit [Abstract]
Tax Cuts And Jobs Act Of 2017, deferred tax asset reduction	$ 100

ULTIMATE SOFTWARE GROUP INC 10-K