Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (USD $) In Thousands, unless otherwise specified	Total	Total Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Treasury Stock	Note Receivable from Stockholder	Accumulated Deficit	Non-controlling Interest	Series A convertible preferred stock	Series A-2 convertible preferred stock	Series B convertible preferred stock	Series C convertible preferred stock
Balance at Dec. 31, 2008 (as reported)	$ (57,763)						$ (53,289)
Balance (Correction of prior years cumulative error)	(906)						(906)
Balance at Dec. 31, 2008	(58,669)	112,690			(4,575)	(100)	(54,195)	201	20,747	6,393	12,918	72,632
Balance (in shares) at Dec. 31, 2008			5,736						5,053	1,105	3,433	10,983
Increase (Decrease) in Stockholders' Equity
Accretion of convertible preferred stock	(5,259)	5,259		(779)			(4,480)		758	238	515	3,748
Issuance of common stock upon exercise of common stock warrants	3			3
Issuance of common stock upon exercise of common stock warrants (in shares)			71
Issuance of common stock upon exercise of stock options	36			36
Issuance of common stock upon exercise of stock options (in shares)			26
Stock-based compensation expense	740			740
Interest accrued on note receivable from stockholder	(3)					(3)
Non-controlling interest distribution	(398)							(398)
Net income	1,142						748	394
Balance at Dec. 31, 2009	(62,408)	117,949			(4,575)	(103)	(57,927)	197	21,505	6,631	13,433	76,380
Balance (in shares) at Dec. 31, 2009			5,833						5,053	1,105	3,433	10,983
Increase (Decrease) in Stockholders' Equity
Accretion of convertible preferred stock	(5,020)	5,020		(869)			(4,151)		758	237	515	3,510
Issuance of common stock upon exercise of stock options	2			2
Issuance of common stock upon exercise of stock options (in shares)			2
Stock-based compensation expense	867			867
Non-controlling interest distribution	(547)							(547)
Net income	16,121						15,574	547
Balance at Dec. 31, 2010	(50,985)	122,969			(4,575)	(103)	(46,504)	197	22,263	6,868	13,948	79,890
Balance (in shares) at Dec. 31, 2010			5,835						5,053	1,105	3,433	10,983
Increase (Decrease) in Stockholders' Equity
Accretion of convertible preferred stock	(1,633)	1,633					(1,633)		258	82	176	1,117
Issuance of common stock upon conversion of preferred stock	124,602	(124,602)	2	124,600					(22,521)	(6,950)	(14,124)	(81,007)
Issuance of common stock upon conversion of preferred stock (in shares)			22,846						(5,053)	(1,105)	(3,433)	(10,983)
Issuance of common stock upon initial public offering	48,297		1	48,296
Issuance of common stock upon initial public offering (in shares)			3,847
Issuance of common stock upon exercise and conversion of preferred stock warrants	272			272
Issuance of common stock upon exercise and conversion of preferred stock warrants (in shares)			20
Issuance of common stock upon exercise of common stock warrants (in shares)			21
Issuance of common stock upon exercise of stock options	1,028			1,028
Issuance of common stock upon exercise of stock options (in shares)			1,015
Offering costs	(2,596)			(2,596)
Stock-based compensation expense	3,450			3,450
Retirement of treasury stock				(4,575)	4,575
Forgiveness of note receivable from stockholder	103					103
Excess tax benefits from stock-based compensation	246			246
Non-controlling interest distribution	(642)							(642)
Net income	6,937						6,295	642
Balance at Dec. 31, 2011	$ 129,079	$ 0	$ 3	$ 170,721			$ (41,842)	$ 197
Balance (in shares) at Dec. 31, 2011			33,584