Fair Value Measurements - Derivatives' Cash Flow Hedging Relationships (Detail) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Amount of after tax of gain/(loss) recognized in Other Comprehensive Income on Derivatives (effective portion)		$ (4,096,000)	$ (3,015,000)
Pre-tax amount of gain/(loss) reclassified from Accumulated Other Comprehensive Income into Income (effective portion)	$ (500,000)	(927,000)
Interest Expense [Member] | Forward Starting Interest Rate Swap Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of after tax of gain/(loss) recognized in Other Comprehensive Income on Derivatives (effective portion)		(4,096,000)	$ (3,015,000)
Pre-tax amount of gain/(loss) reclassified from Accumulated Other Comprehensive Income into Income (effective portion)		$ (927,000)