Derivative Financial Instruments - Impact of Derivatives on Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative Assets	$ 636	$ 7,808
Fair Value | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Total net derivatives	23,000	30,000
Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative Assets	636	7,808
Derivative Liabilities	(8,636)	(25,937)
Total net derivatives	(8,000)	(18,129)
Interest rate swaps | Trading
Derivatives, Fair Value [Line Items]
Derivative Assets	0	0
Derivative Liabilities	(221)	(1,076)
Total net derivatives	(221)	(1,076)
Interest rate swaps | Cash Flow | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Assets	636	0
Derivative Liabilities	(7,247)	(14,463)
Total net derivatives	(6,611)	(14,463)
Interest rate swaps | Fair Value | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Assets	0	7,808
Derivative Liabilities	(1,168)	(10,398)
Total net derivatives	$ (1,168)	$ (2,590)