Securities - Amortized Cost and Estimated Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Jun. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Available for sale:
Amortized Cost	$ 1,182,686		$ 1,237,433
Gross Unrealized Gains	6,584		686
Gross Unrealized Losses	(84,481)		(135,591)
Fair Value	1,104,789		1,102,528
Allowance for Credit Losses	0		0
Net Carrying Amount	1,104,789		1,102,528
Held to maturity:
Amortized Cost	10,602
Fair Value	10,018		10,456
Allowance for Credit Losses	(43)	$ (47)	(50)	$ (52)	$ (57)	$ (63)
Net Carrying Amount	10,559		11,095
Securities carried at fair value through income:
Fair Value	6,203		6,512
State and municipal securities
Available for sale:
Amortized Cost	324,806		299,642
Gross Unrealized Gains	799		216
Gross Unrealized Losses	(33,021)		(43,882)
Fair Value	292,584		255,976
Allowance for Credit Losses	0		0
Net Carrying Amount	292,584		255,976
Held to maturity:
Amortized Cost	10,602		11,145
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(584)		(689)
Fair Value	10,018		10,456
Allowance for Credit Losses	(43)		(50)
Net Carrying Amount	10,559		11,095
Securities carried at fair value through income:
Amortized Cost	6,200		6,515
Fair Value	6,203		6,512
Net Carrying Amount	6,203		6,512
Corporate bonds
Available for sale:
Amortized Cost	64,104		83,041
Gross Unrealized Gains	148		445
Gross Unrealized Losses	(2,417)		(5,250)
Fair Value	61,835		78,236
Allowance for Credit Losses	0		0
Net Carrying Amount	61,835		78,236
U.S. treasury and government agency securities
Available for sale:
Amortized Cost	3,847		14,742
Gross Unrealized Gains	1		2
Gross Unrealized Losses	(720)		(939)
Fair Value	3,128		13,805
Allowance for Credit Losses	0		0
Net Carrying Amount	3,128		13,805
Commercial mortgage-backed securities
Available for sale:
Amortized Cost	17,047		49,943
Gross Unrealized Gains	20		0
Gross Unrealized Losses	(1,819)		(5,659)
Fair Value	15,248		44,284
Allowance for Credit Losses	0		0
Net Carrying Amount	15,248		44,284
Residential mortgage-backed securities
Available for sale:
Amortized Cost	476,073		598,380
Gross Unrealized Gains	4,131		8
Gross Unrealized Losses	(31,136)		(57,554)
Fair Value	449,068		540,834
Allowance for Credit Losses	0		0
Net Carrying Amount	449,068		540,834
Commercial collateralized mortgage obligations
Available for sale:
Amortized Cost	83,272		31,263
Gross Unrealized Gains	435		0
Gross Unrealized Losses	(1,121)		(2,697)
Fair Value	82,586		28,566
Allowance for Credit Losses	0		0
Net Carrying Amount	82,586		28,566
Residential collateralized mortgage obligations
Available for sale:
Amortized Cost	213,537		160,422
Gross Unrealized Gains	1,050		15
Gross Unrealized Losses	(14,247)		(19,610)
Fair Value	200,340		140,827
Allowance for Credit Losses	0		0
Net Carrying Amount	$ 200,340		$ 140,827

Origin Bancorp, Inc. 10-Q