Derivative Instruments and Hedging Activities - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2018 USD ($) Swap	Dec. 31, 2017 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Reclassified as interest income, expected during the next 12 months	$ 1,100,000
Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Number of interest rate swaps held | Swap	5
Maturity of interest rate swap	May 14, 2020
Notional amount of interest rate swap	$ 1,000,000,000
Combined Interest Rate Cash Flow Hedges, All Swaps [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Number of interest rate swaps held | Swap	5
Maturity of interest rate swap	May 14, 2020
Notional amount of interest rate swap	$ 1,000,000,000
Not Designated as Hedge Accounting Relationships [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives outstanding	$ 0	$ 0