Fair Values of Derivative Designated as Hedging Instruments Recorded in Consolidated Balance Sheet (Detail) - Interest rate derivatives - Derivatives Designated as Hedging Instruments - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Other current assets
Derivatives, Fair Value [Line Items]
Derivative Assets, Fair Value	$ 7,132	$ 3,590
Other assets
Derivatives, Fair Value [Line Items]
Derivative Assets, Fair Value	13,945	6,566
Other accrued liabilities
Derivatives, Fair Value [Line Items]
Derivative Liabilities, Fair Value		(3,053)
Other long-term liabilities
Derivatives, Fair Value [Line Items]
Derivative Liabilities, Fair Value	$ (377)	$ (971)