Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (loss)
Beginning balance at Dec. 31, 2016	$ 477,347	$ 252,820	$ 232,440	$ (7,913)
Beginning balance, shares at Dec. 31, 2016		22,867,802
Net income	40,554		40,554
Other comprehensive income (loss)	2,685			2,685
Stock option vesting	259	$ 259
Service condition RSU vesting	895	895
Market plus service condition RSU vesting	432	432
Stock options exercised	2,621	$ 2,621
Stock options exercised, shares		145,850
Service condition RSUs released	0
Service condition RSUs released, shares		30,896
Tax benefit from release of service condition RSUs	0
Tax benefit from release of service condition RSUs, shares		18,805
Repurchase of common stock	$ (3,854)	$ (1,191)	(2,663)
Repurchase of common stock, shares	0	(107,390)
Dividends paid	$ (15,131)		(15,131)
Dividends paid, per share	$ 0.66
Ending balance at Dec. 31, 2017	$ 505,808	$ 255,836	255,200	(5,228)
Ending balance, shares at Dec. 31, 2017		22,955,963
Net income	68,320		68,320
Other comprehensive income (loss)	(11,620)			(11,620)
Adoption of ASU | Adoption ASU 2016-01			(62)	62
Adoption of ASU | Adoption ASU 2018-02			1,093	(1,093)
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, shares	100,400	100,400
Service condition RSUs released	$ 0
Service condition RSUs released, shares		35,060
Market plus service condition RSUs released	0
Market plus service conditions RSUs released, shares		25,512
Issuance of common stock	284,437	$ 284,437
Issuance of common stock, shares		7,405,277
Repurchase of common stock	$ (3,969)	$ (1,677)	(2,292)
Repurchase of common stock, shares	(196,566)	(104,989)
Dividends paid	$ (18,769)		(18,769)
Dividends paid, per share	$ 0.70
Ending balance at Dec. 31, 2018	$ 827,373	$ 541,762	303,490	(17,879)
Ending balance, shares at Dec. 31, 2018	30,417,223	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, shares	182,500	182,500
Service condition RSUs released	$ 0
Service condition RSUs released, shares		33,060
Market plus service condition RSUs released	0
Market plus service conditions RSUs released, shares		22,237
Repurchase of common stock	$ (5,108)	$ (2,339)	(2,769)
Repurchase of common stock, shares	0	(131,196)
Dividends paid	$ (24,999)		(24,999)
Dividends paid, per share	$ 0.82
Ending balance at Dec. 31, 2019	$ 906,570	$ 543,998	$ 367,794	$ (5,222)
Ending balance, shares at Dec. 31, 2019	30,523,824	30,523,824