Derivative Financial Instruments - Impact of Derivatives on Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Derivative Assets	$ 25,410		$ 5,238
Derivative Liabilities	(38,063)		(28,688)
Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	25,410	[1],[2]	5,238	[1],[2]
Derivative Liabilities	(38,063)	[1],[2]	(28,688)	[1],[2]
Total net derivatives	(12,653)	[1]	(23,450)	[1]
Interest rate swaps [Member] | Trading
Derivatives, Fair Value [Line Items]
Derivative Assets	1,033	[1],[2]	226	[1],[2]
Derivative Liabilities	(30)	[1],[2]	(1,370)	[1],[2]
Total net derivatives	1,003	[1]	(1,144)	[1]
Interest rate swaps [Member] | Cash Flow | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	0	[1],[2]	0	[1],[2]
Derivative Liabilities	(37,295)	[1],[2]	(21,435)	[1],[2]
Total net derivatives	(37,295)	[1]	(21,435)	[1]
Interest rate swaps [Member] | Fair Value | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	24,377	[1],[2]	5,012	[1],[2]
Derivative Liabilities	(738)	[1],[2]	(5,883)	[1],[2]
Total net derivatives	$ 23,639	[1]	$ (871)	[1]

[1] Fair values reported are exclusive of collateral held and pledged and accrued interest. Assets and liabilities are presented without consideration of master netting agreements. Derivatives are carried on the balance sheet based on net position by counterparty under master netting agreements, and classified in other assets or other liabilities depending on whether in a net positive or negative position.

[2] The following table reconciles gross positions with the impact of master netting agreements to the balance sheet classification: Other Assets Other Liabilities March 31, December 31, March 31, December 31, 2015 2014 2015 2014Gross position $25,410 $5,238 $(38,063) $(28,688)Impact of master netting agreement (11,003) (4,045) 11,003 4,045Derivative values with impact of master netting agreements (as carried on balance sheet) 14,407 1,193 (27,060) (24,643)Cash collateral (held) pledged(1) (3,283) (900) 58,625 72,478Net position $11,124 $293 $31,565 $47,835