Accounts Receivable, net - Summary of Accounts Receivable, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, gross	$ 199,914	$ 285,282
Allowance for uncollectible revenue	(2,463)	(2,213)
Accounts receivable, net	197,451	283,069
Billed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, gross	113,610	203,575
Unbilled [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, gross	$ 86,304	$ 81,707