The Company and Basis of Presentation - Additional Information (Detail)	Sep. 30, 2017
Minimum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Equity method investment, ownership percentage	20.00%
Maximum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Equity method investment, ownership percentage	50.00%
Cost method investment, ownership Percentage	20.00%