Prepaid Expenses and Other Current Assets - Additional Information (Detail) ¥ in Thousands, $ in Thousands	Dec. 31, 2016 CNY (¥)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 CNY (¥)
Prepaid Expenses And Other Current Assets [Line Items]
Prepaid purchase cost	¥ 317,262	$ 45,695	¥ 272,859
Motor Vehicles [Member]
Prepaid Expenses And Other Current Assets [Line Items]
Prepaid purchase cost	¥ 226,419	$ 32,611	¥ 191,341

Amount of asset related to consideration paid in advance for costs that provide economic benefits within a future period of one year or the normal operating cycle, if longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6787-107765

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 10
-Section 05
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=68074540&loc=d3e5879-108316

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Current Assets
-URI http://asc.fasb.org/extlink&oid=6509628

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765

Name:	us-gaap_PrepaidExpenseCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant