Certain Risks and Concentration - Schedule of Consolidated Financial Information of VIEs and VIE's Subsidiaries - Cash Flow (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net cash provided by operating activities	$ 48,202	$ 85,533	$ 59,914
Net cash used in investing activities	(70,546)	(78,352)	(49,490)
Net cash (used in) / provided by financing activities	333,268	2,487	17,692
Net increase in cash and cash equivalents	310,924	9,668	28,116
Variable Interest Entity, Primary Beneficiary [Member]
Net cash provided by operating activities	70,822	92,580	59,379
Net cash used in investing activities	(78,335)	(66,243)	(33,675)
Net cash (used in) / provided by financing activities	856	2,487	(20,632)
Net increase in cash and cash equivalents	$ (6,657)	$ 28,824	$ 5,072

Amount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.

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Amount of cash inflow (outflow) of financing activities, excluding discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) of investing activities, excluding discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

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Amount of cash inflow (outflow) from operating activities, excluding discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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