Derivative Financial Instruments Schedule of outstanding interest rate swaps and caps not designated for hedge accounting (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivative [Line Items]
Total Notional Amount	$ 10,405,957	$ 13,138,667
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Gain	9,855	17,062
Derivative Asset, Loss	(24,757)	(23,087)
Not Designated as Hedging Instrument [Member] | Customer Position [Member]
Derivative [Line Items]
Number of Instruments	269	235
Total Notional Amount	1,931,021	1,563,728
Derivative Asset, Gain	35,207	29,004
Derivative Liability, Loss	(5,534)	(11,175)
Net	29,673	17,829
Not Designated as Hedging Instrument [Member] | Customer Position [Member] | Other Assets [Member] | Commercial loan interest rate derivatives [Member]
Derivative [Line Items]
Number of Instruments	196	159
Total Notional Amount	1,245,748	915,272
Derivative Asset, Gain	35,207	29,004
Derivative Asset, Loss	0	0
Net	35,207	29,004
Not Designated as Hedging Instrument [Member] | Customer Position [Member] | Other Liabilities [Member] | Commercial loan interest rate derivatives [Member]
Derivative [Line Items]
Number of Instruments	73	76
Total Notional Amount	685,273	648,456
Derivative Liability, Gain	0	0
Derivative Liability, Loss	(5,534)	(11,175)
Net	(5,534)	(11,175)
Not Designated as Hedging Instrument [Member] | Counterparty Position [Member]
Derivative [Line Items]
Number of Instruments	273	243
Total Notional Amount	9,930,957	12,763,667
Derivative Asset, Gain	9,855	17,094
Derivative Liability, Loss	(24,757)	(23,119)
Net	(14,902)	(6,025)
Not Designated as Hedging Instrument [Member] | Counterparty Position [Member] | Other Assets [Member] | Commercial loan interest rate derivatives [Member]
Derivative [Line Items]
Number of Instruments	84	111
Total Notional Amount	605,806	914,044
Derivative Asset, Gain	4,019	8,944
Derivative Asset, Loss	(2,625)	(2,766)
Net	1,394	6,178
Not Designated as Hedging Instrument [Member] | Counterparty Position [Member] | Other Liabilities [Member] | Commercial loan interest rate derivatives [Member]
Derivative [Line Items]
Number of Instruments	179	118
Total Notional Amount	1,325,151	649,623
Derivative Liability, Gain	5,828	8,118
Derivative Liability, Loss	(21,682)	(20,094)
Net	(15,854)	(11,976)
Not Designated as Hedging Instrument [Member] | Counterparty Position [Member] | Other Liabilities [Member] | Fed Funds futures [Member]
Derivative [Line Items]
Number of Instruments	10	14
Total Notional Amount	8,000,000	11,200,000
Derivative Liability, Gain	8	32
Derivative Liability, Loss	(450)	(259)
Net	$ (442)	$ (227)