Derivative Financial Instruments - Impact of Derivatives on Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Derivative Assets	$ 15,189	$ 5,238
Derivative Liabilities	(19,710)	(28,688)
Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative Assets	15,189	5,238
Derivative Liabilities	(19,710)	(28,688)
Total net derivatives	(4,521)	(23,450)
Interest rate swaps | Trading
Derivatives, Fair Value [Line Items]
Derivative Assets	1,113	226
Derivative Liabilities	(2)	(1,370)
Total net derivatives	1,111	(1,144)
Interest rate swaps | Cash Flow | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Assets	0	0
Derivative Liabilities	(18,974)	(21,435)
Total net derivatives	(18,974)	(21,435)
Interest rate swaps | Fair Value | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Assets	14,076	5,012
Derivative Liabilities	(734)	(5,883)
Total net derivatives	$ 13,342	$ (871)