Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Beginning balance at Dec. 31, 2018	$ 357,989	$ 39	$ 330,572	$ (586)	$ 27,964
Balance (in shares) at Dec. 31, 2018		39,015,034
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,266				13,266
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	896			896
Issuance of common stock upon exercise of stock options	4,047		4,047
Issuance of common stock upon exercise of stock options (shares)		152,164
Stock Repurchased During Period, Shares		(94,090)
Repurchase of common stock	(7,871)		(1,129)		(6,742)
Adjustment To Additional Paid In Capital, Share-Based Compensation, Taxes Related To Net Share Settlements Of Equity Awards		(38,877)
Issuance of common stock upon vesting of restricted stock units (in shares)		99,601
Taxes from release of the restricted share units	(3,367)		(3,367)
Stock-based compensation	8,443		8,443
Ending balance at Mar. 31, 2019	373,403	$ 39	338,566	310	34,488
Balance (in shares) at Mar. 31, 2019		39,133,832
Beginning balance at Dec. 31, 2018	357,989	$ 39	330,572	(586)	27,964
Balance (in shares) at Dec. 31, 2018		39,015,034
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,498				29,498
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1,826
Change in unrealized loss on investments	1,422
Ending balance at Jun. 30, 2019	383,598	$ 39	345,637	1,240	36,682
Balance (in shares) at Jun. 30, 2019		39,224,075
Beginning balance at Mar. 31, 2019	373,403	$ 39	338,566	310	34,488
Balance (in shares) at Mar. 31, 2019		39,133,832
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	16,232				16,232
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	930			930
Issuance of common stock upon exercise of stock options	4,944		4,944
Issuance of common stock upon exercise of stock options (shares)		192,687
Stock Repurchased During Period, Shares		(183,948)
Repurchase of common stock	(16,245)		(2,207)		(14,038)
Adjustment To Additional Paid In Capital, Share-Based Compensation, Taxes Related To Net Share Settlements Of Equity Awards		(45,250)
Issuance of common stock upon vesting of restricted stock units (in shares)		126,754
Taxes from release of the restricted share units	(4,044)		(4,044)
Stock-based compensation	8,378		8,378
Ending balance at Jun. 30, 2019	383,598	$ 39	345,637	1,240	36,682
Balance (in shares) at Jun. 30, 2019		39,224,075
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained Earnings (Accumulated Deficit)	23,194
Beginning balance at Dec. 31, 2019	386,803	$ 39	362,408	1,162	23,194
Balance (in shares) at Dec. 31, 2019		39,146,272
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	18,694				18,694
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	391			391
Issuance of common stock upon exercise of stock options	4,714		4,714
Issuance of common stock upon exercise of stock options (shares)		144,989
Stock Repurchased During Period, Shares		(346,250)
Repurchase of common stock	(28,926)		(4,160)		(24,766)
Adjustment To Additional Paid In Capital, Share-Based Compensation, Taxes Related To Net Share Settlements Of Equity Awards		(58,598)
Issuance of common stock upon vesting of restricted stock units (in shares)		138,260
Taxes from release of the restricted share units	(5,000)		(5,000)
Stock-based compensation	10,054		10,054
Ending balance at Mar. 31, 2020	386,730	$ 39	368,016	1,553	17,122
Balance (in shares) at Mar. 31, 2020		39,024,673
Beginning balance at Dec. 31, 2019	386,803	$ 39	362,408	1,162	23,194
Balance (in shares) at Dec. 31, 2019		39,146,272
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	45,013				45,013
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1,273
Change in unrealized loss on investments	$ 1,344
Issuance of common stock upon exercise of stock options (shares)	593,045
Stock Repurchased During Period, Shares	(588,750)
Repurchase of common stock	$ (54,200)
Ending balance at Jun. 30, 2020	407,774	$ 39	384,202	2,435	21,098
Balance (in shares) at Jun. 30, 2020		39,315,337
Beginning balance at Mar. 31, 2020	386,730	$ 39	368,016	1,553	17,122
Balance (in shares) at Mar. 31, 2020		39,024,673
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	26,319				26,319
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	882			882
Issuance of common stock upon exercise of stock options	15,716	$ 1	15,715
Issuance of common stock upon exercise of stock options (shares)		448,056
Stock Repurchased During Period, Shares		(242,500)
Repurchase of common stock	(25,256)	$ (1)	(2,912)		(22,343)
Adjustment To Additional Paid In Capital, Share-Based Compensation, Taxes Related To Net Share Settlements Of Equity Awards		(61,235)
Issuance of common stock upon vesting of restricted stock units (in shares)		146,343
Taxes from release of the restricted share units	(6,115)		(6,115)
Stock-based compensation	9,498		9,498
Ending balance at Jun. 30, 2020	407,774	$ 39	$ 384,202	$ 2,435	$ 21,098
Balance (in shares) at Jun. 30, 2020		39,315,337
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained Earnings (Accumulated Deficit)	$ 21,098