Derivatives - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments [Line Items]
Repayments of Secured Debt		$ 150,000	$ 280,327
Estimate increase to interest expense	$ 300	300
Carrying Value Of Net Losses Associated With Interest Rate Swaps	1,000	1,000
Fair value of derivatives in a net liability position	(445)	(445)
Termination value	$ 400	$ 400
Interest rate swaps [Member]
Derivative Instruments [Line Items]
Number of derivative, interest rate swap agreement	30	30
Derivative, Weighted average interest rate	1.35%	1.35%
Derivative, notional amount	$ 749,600	$ 749,600
Interest Rate Swap Member Forward Starting [Member]
Derivative Instruments [Line Items]
Number of derivative, interest rate swap agreement	1	1
Derivative, Weighted average interest rate	1.42%	1.42%
Derivative, notional amount	$ 48,000	$ 48,000
Maturity Date	Feb. 01, 2021
Interest Rate Swap Twelve [Member]
Derivative Instruments [Line Items]
Maturity Date		Jan. 02, 2019
Settled Interest Rate Swaps [Member]
Derivative Instruments [Line Items]
Amortization Period of Deferred Gain (Loss) on Discontinuation of Fair Value Hedge		10 years