Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive income (loss)	Treasury stock
Beginning Balance at Dec. 31, 2016	$ 15,696
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income	2,337
Ending Balance at Dec. 31, 2017	18,033
Beginning Balance at Dec. 31, 2016	417,019	$ 4	$ 1,510,152	$ (1,092,756)	$ (381)
Beginning balance (in shares) at Dec. 31, 2016		41,845
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued for stock options and restricted stock units	40,272	$ 1	40,271
Common stock issued for stock options and restricted stock units (in shares)		4,382
Common stock issued for employee stock purchase plan	1,429		1,429
Common stock issued for employee stock purchase plan (in shares)		139
Other comprehensive income (loss)	377				377
Stock-based compensation	64,344		12,801	51,543
Tax payments from shares withheld for equity awards	(9,095)		(9,095)
Other	2		2
Net income	27,039			27,039
Ending Balance at Dec. 31, 2017	541,387	$ 5	1,555,560	(1,014,174)	(4)
Ending balance (in shares) at Dec. 31, 2017		46,366
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income	935
Adjustment of redeemable noncontrolling interests to redemption value	5,977
Ending Balance at Dec. 31, 2018	24,945
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued for stock options and restricted stock units	13,151	$ 0	13,151
Common stock issued for stock options and restricted stock units (in shares)		1,577
Common stock issued for employee stock purchase plan	2,100		2,100
Common stock issued for employee stock purchase plan (in shares)		101
Other comprehensive income (loss)	(442)				(442)
Stock-based compensation	13,253		13,253	0
Tax payments from shares withheld for equity awards	(8,362)		(8,362)
Adjustment of redeemable noncontrolling interests to redemption value	(5,977)		(5,977)
Net income	50,634			50,634
Ending Balance at Dec. 31, 2018	$ 607,595	$ 5	1,569,725	(961,689)	(446)
Ending balance (in shares) at Dec. 31, 2018	48,044	48,044
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income	$ 0
Adjustment of redeemable noncontrolling interests to redemption value	(2,517)
Ending Balance at Dec. 31, 2019	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued for stock options and restricted stock units	4,387		4,387
Common stock issued for stock options and restricted stock units (in shares)		906
Common stock issued for employee stock purchase plan	2,212		2,212
Common stock issued for employee stock purchase plan (in shares)		109
Stock repurchased and retired during period (in shares)		0
Stock repurchases (in shares)						(1,306)
Stock repurchases						$ (28,399)
Stock repurchased and retired during the period	28,399
Other comprehensive income (loss)	174				174
Stock-based compensation	16,300		16,300
Tax payments from shares withheld for equity awards	(5,652)		(5,652)
Reclassification of mandatorily redeemable noncontrolling interests	(22,428)
Net income	48,148			48,148
Ending Balance at Dec. 31, 2019	$ 643,515	$ 5	$ 1,586,972	$ (914,791)	$ (272)	$ (28,399)
Ending balance (in shares) at Dec. 31, 2019	47,753	49,059				(1,306)