Redeemable Convertible Preferred Stock and Shareholders' Equity - Summary of Redeemable Convertible Preferred Stock (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Increase (Decrease) in Temporary Equity
Accretion of dividends	$ 0	$ 18,391	$ 21,994
Series A Redeemable Convertible Preferred Stock
Increase (Decrease) in Temporary Equity
Beginning balance		1,358	802
Accretion of dividends		52	556
Conversion to common stock		(1,410)
Ending balance		0	1,358
Beginning balance, shares		705,400	705,400
Conversion to common stock, shares		(705,400)
Ending balance, shares		0	705,400
Series B Redeemable Convertible Preferred Stock
Increase (Decrease) in Temporary Equity
Beginning balance		669	639
Accretion of dividends		19	30
Conversion to common stock		(688)
Ending balance		0	669
Beginning balance, shares		694,000	694,000
Conversion to common stock, shares		(694,000)
Ending balance, shares		0	694,000
Series B-1 Redeemable Convertible Preferred Stock
Increase (Decrease) in Temporary Equity
Beginning balance		1,360	1,300
Accretion of dividends		37	60
Conversion to common stock		(1,397)
Ending balance		0	1,360
Beginning balance, shares		1,212,360	1,212,360
Conversion to common stock, shares		(1,212,360)
Ending balance, shares		0	1,212,360
Series C Redeemable Convertible Preferred Stock
Increase (Decrease) in Temporary Equity
Beginning balance		7,134	6,729
Accretion of dividends		266	405
Conversion to common stock		(7,400)
Ending balance		0	7,134
Beginning balance, shares		4,546,360	4,546,360
Conversion to common stock, shares		(4,546,360)
Ending balance, shares		0	4,546,360
Series C-1 Redeemable Convertible Preferred Stock
Increase (Decrease) in Temporary Equity
Beginning balance		34,201	32,264
Accretion of dividends		1,272	1,937
Conversion to common stock		(35,473)
Ending balance		0	34,201
Beginning balance, shares		15,934,528	15,934,528
Conversion to common stock, shares		(15,934,528)
Ending balance, shares		0	15,934,528
Series C-2 Redeemable Convertible Preferred Stock
Increase (Decrease) in Temporary Equity
Beginning balance		44,512	41,987
Accretion of dividends		1,660	2,525
Conversion to common stock		(46,172)
Ending balance		0	44,512
Beginning balance, shares		18,617,020	18,617,020
Conversion to common stock, shares		(18,617,020)
Ending balance, shares		0	18,617,020
Series C-3 Redeemable Convertible Preferred Stock
Increase (Decrease) in Temporary Equity
Beginning balance		29,770	28,082
Accretion of dividends		1,103	1,688
Conversion to common stock		(30,873)
Ending balance		0	29,770
Beginning balance, shares		13,297,872	13,297,872
Conversion to common stock, shares		(13,297,872)
Ending balance, shares		0	13,297,872
Series D Redeemable Convertible Preferred Stock
Increase (Decrease) in Temporary Equity
Beginning balance		76,252	71,924
Accretion of dividends		2,827	4,328
Conversion to common stock		(79,078)
Settlement of fractional shares upon conversion to common stock		(1)
Ending balance		0	76,252
Beginning balance, shares		19,803,685	19,803,685
Conversion to common stock, shares		(19,803,685)
Settlement of fractional shares upon conversion to common stock, shares		0
Ending balance, shares		0	19,803,685
Series E Redeemable Convertible Preferred Stock
Increase (Decrease) in Temporary Equity
Beginning balance		211,403	117,954
Issuance of shares			83,000
Accretion of dividends		7,931	10,465
Stock issuance costs			(16)
Conversion to common stock		(219,332)
Settlement of fractional shares upon conversion to common stock		(2)
Ending balance		0	211,403
Beginning balance, shares		38,095,239	22,285,716
Issuance of shares, shares			15,809,523
Conversion to common stock, shares		(38,095,239)
Settlement of fractional shares upon conversion to common stock, shares		0
Ending balance, shares		0	38,095,239
Series F Redeemable Convertible Preferred Stock
Increase (Decrease) in Temporary Equity
Beginning balance		0
Issuance of shares		150,000
Accretion of dividends		3,224
Stock issuance costs		(3,148)
Conversion to common stock		(150,075)
Settlement of fractional shares upon conversion to common stock		(1)
Ending balance		$ 0
Beginning balance, shares		0
Issuance of shares, shares		19,047,619
Conversion to common stock, shares		(19,047,619)
Settlement of fractional shares upon conversion to common stock, shares		0
Ending balance, shares		0

The value of the stock converted in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Publisher FASB

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The number of securities classified as temporary equity that have been issued and are held by the entity's shareholders. Securities outstanding equals securities issued minus securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.27(b))

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

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