Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjusted Balance	Common Stock	Common Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated Other Comprehensive Income (loss)	Accumulated Other Comprehensive Income (loss) Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (loss) Cumulative Effect, Period of Adoption, Adjusted Balance
Beginning balance at Dec. 31, 2017	$ 505,808			$ 255,836		$ 255,200			$ (5,228)
Beginning balance (Adoption ASU 2016-01) at Dec. 31, 2017		$ 0					$ (62)			$ 62
Beginning balance (Adoption ASU 2018-02) at Dec. 31, 2017		0					1,093			$ (1,093)
Beginning balance (in shares) at Dec. 31, 2017				22,955,963
Net income	68,320					68,320
Other comprehensive income (loss)	(11,620)								(11,620)
Stock option vesting	75			$ 75
Service condition RSU vesting	1,017			1,017
Market plus service condition RSU vesting	370			370
Stock options exercised	1,704			$ 1,704
Stock options exercised (in shares)				100,400
Service condition RSUs released (in shares)				35,060
Tax benefit from release of service condition RSUs (in shares)				25,512
Issuance of common stock	284,437			$ 284,437
Issuance of common stock (in shares)				7,405,277
Repurchase of common stock	(3,969)			$ (1,677)		(2,292)
Repurchase of common stock (in shares)				(104,989)
Dividends paid	(18,769)					(18,769)
Ending balance at Dec. 31, 2018	827,373			$ 541,762		303,490			(17,879)
Ending balance (in shares) at Dec. 31, 2018				30,417,223
Net income	92,072					92,072
Other comprehensive income (loss)	12,657								12,657
Service condition RSU vesting	1,161			$ 1,161
Market plus service condition RSU vesting	493			493
Stock options exercised	$ 2,921			$ 2,921
Stock options exercised (in shares)	182,500			182,500
Service condition RSUs released (in shares)				33,060
Market plus service conditions RSUs released (in shares)				22,237
Repurchase of common stock	$ (5,108)			$ (2,339)		(2,769)
Repurchase of common stock (in shares)				(131,196)
Dividends paid	(24,999)					(24,999)
Ending balance at Dec. 31, 2019	$ 906,570	$ (12,983)	$ 893,587	$ 543,998	$ 543,998	367,794	$ (12,983)	$ 354,811	(5,222)		$ (5,222)
Ending balance (in shares) at Dec. 31, 2019	30,523,824			30,523,824	30,523,824
Net income	$ 64,814					64,814
Other comprehensive income (loss)	17,502								17,502
Service condition RSU vesting	1,390			$ 1,390
Market plus service condition RSU vesting	646			646
Stock options exercised	$ 547			$ 547
Stock options exercised (in shares)	32,000			32,000
Service condition RSUs released (in shares)				34,388
Market plus service conditions RSUs released (in shares)				20,265
Repurchase of common stock	$ (27,069)			$ (15,746)		(11,323)
Repurchase of common stock (in shares)				(883,263)
Dividends paid	(26,303)					(26,303)
Ending balance at Dec. 31, 2020	$ 925,114			$ 530,835		$ 381,999			$ 12,280
Ending balance (in shares) at Dec. 31, 2020	29,727,214			29,727,214