Common Stock and Preferred Stock - Summary of Preferred Stock Activity (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Temporary Equity [Line Items]
Beginning balance	$ 614,378	$ 551,452	$ 453,385
Allocation of embedded derivative upon issuance of preferred stock			(6,018)
Preferred stock return	29,277	52,427	31,331
Accretion of preferred stock	5,285	10,499	10,181
Conversion to common stock upon the IPO	(648,940)
Ending balance		614,378	551,452
January 28, 2011 funding [Member]
Temporary Equity [Line Items]
Preferred stock funding			38,095
June 30, 2011 funding [Member]
Temporary Equity [Line Items]
Preferred stock funding			24,478
Class A Preferred Stock [Member]
Temporary Equity [Line Items]
Beginning balance	174,199	152,689	80,278
Allocation of embedded derivative upon issuance of preferred stock			(6,018)
Preferred stock return	11,219	19,505	13,943
Accretion of preferred stock	1,005	2,005	1,913
Conversion to common stock upon the IPO	(186,423)
Ending balance		174,199	152,689
Class A Preferred Stock [Member] \| January 28, 2011 funding [Member]
Temporary Equity [Line Items]
Preferred stock funding			38,095
Class A Preferred Stock [Member] \| June 30, 2011 funding [Member]
Temporary Equity [Line Items]
Preferred stock funding			24,478
Class B Preferred Stock [Member]
Temporary Equity [Line Items]
Beginning balance	285,035	250,572	231,559
Preferred stock return	18,058	32,922	17,388
Accretion of preferred stock	763	1,541	1,625
Conversion to common stock upon the IPO	(303,856)
Ending balance		285,035	250,572
Junior Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Beginning balance	155,144	148,191	141,548
Allocation of embedded derivative upon issuance of preferred stock
Accretion of preferred stock	3,517	6,953	6,643
Conversion to common stock upon the IPO	(158,661)
Ending balance		$ 155,144	$ 148,191