Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands		Total	Cumulative Effect, Period of Adoption, Adjustment	Preferred Stock	Common Stock		Additional Paid-in Capital	Additional Paid-in Capital Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings	[1]	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	[1]	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock
Beginning balance (in shares) at Dec. 31, 2017				1,200,000	30,686,256	[1]
Beginning balance at Dec. 31, 2017		$ 287,147		$ 12	$ 307	[1]	$ 256,108		$ 23,694				$ 7,026		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		19,590							19,590
Change in unrealized appreciation (depreciation) on available-for-sale securities		(10,036)											(10,036)
Issuance of shares (in shares)	[1]				14,805,128
Issuance of shares		204,215			$ 148	[1]	204,141		(74)
Issuance of shares from equity based awards (in shares)	[1]				352,746
Issuance of shares from equity-based awards		(2,131)			$ 4	[1]	(2,134)		(1)
Retired shares (in shares)	[1]				(769,808)
Retired shares		(11,024)			$ (8)	[1]	(8,218)		(2,798)
Preferred dividends declared		(2,100)							(2,100)
Employee receivables from sale of stock		71					11		60
Stock-based compensation		4,439					4,439
Employee stock purchase plan additions		165					165
Ending balance (in shares) at Dec. 31, 2018				1,200,000	45,074,322	[1]
Ending balance at Dec. 31, 2018		490,336		$ 12	$ 451	[1]	454,512		38,371				(3,010)		0
Ending balance (Accounting Standards Update 2016-01) at Dec. 31, 2018			$ 0								$ (69)			$ 69
Ending balance (Accounting Standards Update 2018-07) at Dec. 31, 2018			$ 306					$ 2,159			$ (1,853)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		28,473							28,473
Change in unrealized appreciation (depreciation) on available-for-sale securities		19,392											19,392
Issuance of shares (in shares)	[1]				6,851,213
Issuance of shares		88,871			$ 68	[1]	88,803
Issuance of shares from equity based awards (in shares)	[1]				53,668
Issuance of shares from equity-based awards		(245)			$ 1	[1]	(246)
Retired shares (in shares)				(1,200,000)	(10,000)	[1]
Retired shares		(30,155)		$ (12)			(30,088)		(55)
Preferred dividends declared		(175)							(175)
Employee receivables from sale of stock		117					6		111
Stock-based compensation		4,688					4,688
Employee stock purchase plan additions		36					36
Performance award adjustment as a result of ASU 2018-07, net of tax		(34)					(238)		204
Ending balance (in shares) at Dec. 31, 2019				0	51,969,203	[1]
Ending balance at Dec. 31, 2019		601,644		$ 0	$ 520	[1]	519,870		64,803				16,451		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		12,601							12,601
Change in unrealized appreciation (depreciation) on available-for-sale securities		12,952											12,952
Issuance of shares from equity based awards (in shares)	[1]				319,926
Issuance of shares from equity-based awards		(1,084)			$ 3	[1]	(1,087)
Open market common share repurchases (in shares)	[1]				(609,613)
Open market common share repurchases		(6,061)													(6,061)
Employee receivables from sale of stock		47					3		44
Stock-based compensation		4,321					4,321
Employee stock purchase plan additions		42					42
Ending balance (in shares) at Dec. 31, 2020				0	51,679,516	[1]
Ending balance at Dec. 31, 2020		$ 624,428		$ 0	$ 523	[1]	$ 522,911		$ 77,652				$ 29,403		$ (6,061)

[1] (1) Share data has been adjusted to reflect a 2-for-1 stock split effected in the form of a dividend on December 21, 2018.