Derivatives and Fair Value Measurements - Fair Values of Swaps in Condensed Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Asset derivatives not designated as hedging instruments	$ 3,714	$ 4
Liability derivatives not designated as hedging instruments	(393)	(5,490)
Net total not designated as hedging instruments	3,321	(5,486)
Swaps [Member] | Deferred Charges and Other Assets [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives not designated as hedging instruments	481
Liability derivatives not designated as hedging instruments	0
Net total not designated as hedging instruments	481
Swaps [Member] | Prepaids and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives not designated as hedging instruments	3,100
Liability derivatives not designated as hedging instruments	(13)
Net total not designated as hedging instruments	3,087
Swaps [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives not designated as hedging instruments	133	0
Liability derivatives not designated as hedging instruments	(380)	(4,267)
Net total not designated as hedging instruments	$ (247)	(4,267)
Swaps [Member] | Other Deferred Credits [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives not designated as hedging instruments		4
Liability derivatives not designated as hedging instruments		(1,223)
Net total not designated as hedging instruments		$ (1,219)