Certain Risks and Concentration - Schedule of Consolidated Financial Information of VIEs and VIE's Subsidiaries - Balance sheet (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 404,275	$ 93,906	$ 81,906	$ 53,349
Short-term investments	29,427us-gaap_ShortTermInvestments	40,993us-gaap_ShortTermInvestments
Accounts receivable, net	28,921us-gaap_AccountsReceivableNetCurrent	35,275us-gaap_AccountsReceivableNetCurrent
Due from related parties	22us-gaap_DueFromRelatedPartiesCurrent	85us-gaap_DueFromRelatedPartiesCurrent
Deferred tax assets	2,091us-gaap_DeferredTaxAssetsNetCurrent	1,185us-gaap_DeferredTaxAssetsNetCurrent
Prepayments and other current assets	14,560	6,319
Copyrights related to content, current portion	16,013us-gaap_IntangibleAssetsCurrent	16,018us-gaap_IntangibleAssetsCurrent
Total current assets	495,309us-gaap_AssetsCurrent	193,781us-gaap_AssetsCurrent
Non-current assets:
Deferred tax assets	10,862us-gaap_DeferredTaxAssetsNetNoncurrent	9,430us-gaap_DeferredTaxAssetsNetNoncurrent
Property and equipment, net	17,519us-gaap_PropertyPlantAndEquipmentNet	20,208us-gaap_PropertyPlantAndEquipmentNet
Intangible assets, net	20,097	11,958
Goodwill	23,237us-gaap_Goodwill
Prepayments for content copyrights	1,988us-gaap_PrepaidExpenseNoncurrent	3,149us-gaap_PrepaidExpenseNoncurrent
Other long-term prepayments	7,840	6,077
Total assets	580,362us-gaap_Assets	244,403us-gaap_Assets
Current liabilities:
Accounts payables	40,204us-gaap_AccountsPayableCurrent	39,820us-gaap_AccountsPayableCurrent
Due to a related party	84us-gaap_DueToRelatedPartiesCurrent	225us-gaap_DueToRelatedPartiesCurrent
Deferred revenue and income, current portion	28,294us-gaap_DeferredRevenueCurrent	29,352us-gaap_DeferredRevenueCurrent
Accrued liabilities and other payables	31,415	33,407
Total current liabilities	102,551us-gaap_LiabilitiesCurrent	105,385us-gaap_LiabilitiesCurrent
Non-currentliabilities:
Deferred revenue and income, non-current portion	7,294us-gaap_DeferredRevenueNoncurrent	9,190us-gaap_DeferredRevenueNoncurrent
Total liabilities	123,341us-gaap_Liabilities	124,835us-gaap_Liabilities
Variable Interest Entity, Primary Beneficiary [Member]
Current assets:
Cash and cash equivalents	43,849	50,663
Short-term investments	28,575	31,298
Accounts receivable, net	29,248	35,592
Due from related parties	6	85
Deferred tax assets	1,358	750
Prepayments and other current assets	10,819	11,403
Copyrights related to content, current portion	15,333	14,230
Total current assets	129,188	144,021
Non-current assets:
Equity method investments	5,498	2,949
Deferred tax assets	8,262	6,756
Property and equipment, net	17,481	20,116
Intangible assets, net	21,632	13,083
Goodwill	23,237
Prepayments for content copyrights	1,694	2,483
Other long-term prepayments	5,852	2,554
Total non-current assets	83,656	47,941
Total assets	212,844	191,962
Current liabilities:
Accounts payables	49,771	62,603
Due to a related party	84	225
Deferred revenue and income, current portion	28,083	29,352
Income tax payable	2,554	2,581
Accrued liabilities and other payables	86,323	49,265
Total current liabilities	166,815	144,026
Non-currentliabilities:
Deferred revenue and income, non-current portion	6,452	9,190
Total non-current liabilities	6,452	9,190
Total liabilities	$ 173,267	$ 153,216

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19

-Subparagraph a

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(a))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682