Consolidated Statement of Changes in Stockholders’ Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Balance at beginning of period (in shares) at Dec. 31, 2017		121,769,238
Balance at beginning of period at Dec. 31, 2017	$ 396,894	$ 122	$ 499,441	$ (96,290)	$ (6,379)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	6,704		6,704
Exercise of vested options (in shares)		887,906
Exercise of vested options	10,249	$ 1	10,248
Issuance of convertible senior notes, net of issuance costs and taxes	54,184		54,184
Purchase of capped call, net of taxes	(26,243)		(26,243)
Vesting of restricted stock units, net of shares withheld (in shares)		104,849
Vesting of restricted stock units, net of shares withheld	(1,780)		(1,780)
Stock repurchase (in shares)		(2,807,393)
Stock repurchase	(68,586)	$ (3)		(68,583)
Other comprehensive (loss) income	98				98
Net income	12,967			12,967
Balance at period end (in shares) at Mar. 31, 2018		119,954,600
Balance at period end at Mar. 31, 2018	$ 384,487	$ 120	542,554	(151,906)	(6,281)
Balance at beginning of period (in shares) at Dec. 31, 2018	119,771,702	119,771,702
Balance at beginning of period at Dec. 31, 2018	$ 400,898	$ 120	562,033	(153,442)	(7,813)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	$ 8,616		8,616
Exercise of vested options (in shares)	534,693	534,693
Exercise of vested options	$ 5,930	$ 1	5,929
Vesting of restricted stock units, net of shares withheld (in shares)		159,403
Vesting of restricted stock units, net of shares withheld	$ (5,672)		(5,672)
Stock repurchase (in shares)	(532,412)	(532,412)
Stock repurchase	$ (27,492)	$ (1)		(27,491)
Other comprehensive (loss) income	(962)				(962)
Net income	$ 31,579			31,579
Balance at period end (in shares) at Mar. 31, 2019	119,933,386	119,933,386
Balance at period end at Mar. 31, 2019	$ 420,013	$ 120	$ 570,906	$ (142,238)	$ (8,775)