Basis of Presentation - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
Equity Method Investments [Member]
Accounting Policies [Line Items]
Economic interest in unconsolidated investments in voting rights entities, minimum	20.00%
Economic interest in unconsolidated investments in voting rights entities, maximum	50.00%
Cost Method Investments [Member]
Accounting Policies [Line Items]
Economic interest in unconsolidated investments in voting rights entities, Ownership less than	20.00%