Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock and paid-in capital	Retained earnings	Treasury stock	Shares issued
Beginning balance at Dec. 31, 2016		$ 345,984	$ 326,110	$ (115,484)
Beginning balance (in shares) at Dec. 31, 2016				12,414,078	95,966,852
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options		2,720
Exercise of stock options (in shares)	172,326				172,326
Stock-based compensation expense		24,143
Vesting of restricted stock units, net of shards withheld for		(3,161)
Vesting of restricted stock awards and units, net of shares withheld for employee tax (in shares)					397,073
Net income	$ 40,054		40,054
Purchase of treasury stock				$ (14,137)
Purchase of treasury stock (in shares)				865,315
Ending balance at Dec. 31, 2017	$ 606,229	369,686	366,164	$ (129,621)
Ending balance (in shares) at Dec. 31, 2017				13,279,393	96,536,251
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options		38,362
Exercise of stock options (in shares)	2,017,442				2,017,442
Stock-based compensation expense		21,507
Vesting of restricted stock units, net of shards withheld for		(2,818)
Vesting of restricted stock awards and units, net of shares withheld for employee tax (in shares)					370,808
Net income	$ 54,989		54,989
Purchase of treasury stock				$ (5,955)
Purchase of treasury stock (in shares)				383,801
Ending balance at Dec. 31, 2018	$ 713,396	426,737	422,235	$ (135,576)
Ending balance (in shares) at Dec. 31, 2018				13,663,194	98,924,501
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options		39,332
Exercise of stock options (in shares)	2,435,648				2,435,648
Stock-based compensation expense		21,901
Vesting of restricted stock units, net of shards withheld for		(6,988)
Vesting of restricted stock awards and units, net of shares withheld for employee tax (in shares)					406,319
Net income	$ 87,224		87,224
Ending balance at Dec. 31, 2019	$ 854,865	$ 480,982	$ 509,459
Ending balance (in shares) at Dec. 31, 2019				13,663,194	101,766,468