Derivative Instruments and Hedging Activities - Gains (Losses) Related to Interest Rate Derivatives Designated as Hedges of Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Gain Loss On Fair Value Hedges Recognized In Earnings [Line Items]
Interest income	$ 136,338	$ 133,966	$ 267,417	$ 266,965
Interest expense	39,745	42,483	78,759	85,480
Designated as Fair Value Hedge [Member] | Derivative Interest Rate Swaps [Member]
Gain Loss On Fair Value Hedges Recognized In Earnings [Line Items]
Interest income	(49)	425	(73)	522
Interest expense	2,856	(134)	5,832	(274)
Designated as Fair Value Hedge [Member] | Derivatives Designated as Hedging Instruments [Member]
Gain Loss On Fair Value Hedges Recognized In Earnings [Line Items]
Interest income	49	(425)	73	(522)
Interest expense	$ (2,859)	$ 136	$ (5,800)	$ 279