Derivatives - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Derivative Instruments [Line Items]
Estimate increase to interest expense	$ 5.1
Derivative, notional amount	$ 1,048.2
Interest Rate	1.83%
Carrying Value Of Net Losses Associated With Interest Rate Swaps	$ 0.2
Interest Rate Swap [Member]
Derivative Instruments [Line Items]
Derivative, Weighted average interest rate	1.55%
Derivative, notional amount	$ 798.2
Interest Rate Forward Starting Swaps 2023 Maturity [Member]
Derivative Instruments [Line Items]
Derivative, notional amount	$ 250.0
Interest Rate	2.71%
Settled Interest Rate Swaps [Member]
Derivative Instruments [Line Items]
Amortization Period of Deferred Gain (Loss) on Discontinuation of Fair Value Hedge	10 years