Loans and Allowances for Credit Losses Part 2 (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	$ 11,961,144	$ 11,417,009	$ 12,177,046
Individually measured for impairment, recorded investment	132,420	160,435	134,410
Total	12,093,564	11,577,444	12,311,456
Related allowance [Abstract]
Collectively measured for impairment, related allowance	162,126	197,522	167,087
Individually measured for impairment, related allowance	1,027	2,337	4,233
Total measured for impairment, related allowance	205,965	244,209
Allowance for loan losses [Roll Forward]
Beginning balance	215,507	253,481
Provision for loan losses	(7,190)	(787)
Loans charged off	(8,909)	(13,674)
Recoveries	6,557	5,189
Ending balance	205,965	244,209
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	1,915	9,261
Provision for off-balance sheet credit losses	(810)	787
Ending balance	1,105	10,048
Total provision for credit losses	(8,000)	0
Commercial [Member]
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	7,398,444	6,881,908	7,617,445
Individually measured for impairment, recorded investment	19,861	61,677	24,467
Total	7,418,305	6,943,585	7,641,912
Related allowance [Abstract]
Collectively measured for impairment, related allowance	66,071	85,508	65,050
Individually measured for impairment, related allowance	348	464	230
Total measured for impairment, related allowance	66,419	85,972
Allowance for loan losses [Roll Forward]
Beginning balance	65,280	83,443
Provision for loan losses	(1,956)	3,517
Loans charged off	(298)	(2,934)
Recoveries	3,393	1,946
Ending balance	66,419	85,972
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	475	7,906
Provision for off-balance sheet credit losses	(70)	456
Ending balance	405	8,362
Total provision for credit losses	(2,026)	3,973
Commercial Real Estate [Member]
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	2,219,985	2,165,824	2,168,373
Individually measured for impairment, recorded investment	65,175	86,475	60,626
Total	2,285,160	2,252,299	2,228,999
Related allowance [Abstract]
Collectively measured for impairment, related allowance	48,270	61,098	51,775
Individually measured for impairment, related allowance	258	1,644	3,109
Total measured for impairment, related allowance	48,528	62,742
Allowance for loan losses [Roll Forward]
Beginning balance	54,884	67,034
Provision for loan losses	(2,680)	1,121
Loans charged off	(4,800)	(6,725)
Recoveries	1,124	1,312
Ending balance	48,528	62,742
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	1,353	1,250
Provision for off-balance sheet credit losses	(735)	325
Ending balance	618	1,575
Total provision for credit losses	(3,415)	1,446
Residential Mortgage [Member]
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	1,967,238	1,961,414	1,998,432
Individually measured for impairment, recorded investment	45,212	7,512	46,608
Total	2,012,450	1,968,926	2,045,040
Related allowance [Abstract]
Collectively measured for impairment, related allowance	39,923	34,484	40,934
Individually measured for impairment, related allowance	299	229	769
Total measured for impairment, related allowance	40,222	34,713
Allowance for loan losses [Roll Forward]
Beginning balance	41,703	39,207
Provision for loan losses	(274)	(3,119)
Loans charged off	(1,779)	(1,786)
Recoveries	572	411
Ending balance	40,222	34,713
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	78	91
Provision for off-balance sheet credit losses	(6)	(9)
Ending balance	72	82
Total provision for credit losses	(280)	(3,128)
Consumer [Member]
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	375,477	407,863	392,796
Individually measured for impairment, recorded investment	2,172	4,771	2,709
Total	377,649	412,634	395,505
Related allowance [Abstract]
Collectively measured for impairment, related allowance	7,862	16,432	9,328
Individually measured for impairment, related allowance	122	0	125
Total measured for impairment, related allowance	7,984	16,432
Allowance for loan losses [Roll Forward]
Beginning balance	9,453	17,447
Provision for loan losses	(905)	(306)
Loans charged off	(2,032)	(2,229)
Recoveries	1,468	1,520
Ending balance	7,984	16,432
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	9	14
Provision for off-balance sheet credit losses	1	15
Ending balance	10	29
Total provision for credit losses	(904)	(291)
Total Portfolio Segment Allocation [Member]
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	11,961,144	11,417,009	12,177,046
Individually measured for impairment, recorded investment	132,420	160,435	134,410
Total	12,093,564	11,577,444	12,311,456
Related allowance [Abstract]
Collectively measured for impairment, related allowance	162,126	197,522	167,087
Individually measured for impairment, related allowance	1,027	2,337	4,233
Total measured for impairment, related allowance	163,153	199,859	171,320
Allowance for loan losses [Roll Forward]
Beginning balance			171,320
Ending balance	163,153	199,859	171,320
Nonspecific allowance [Member]
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	0	0	0
Individually measured for impairment, recorded investment	0	0	0
Total	0	0	0
Related allowance [Abstract]
Collectively measured for impairment, related allowance	0	0	0
Individually measured for impairment, related allowance	0	0	0
Total measured for impairment, related allowance	42,812	44,350
Allowance for loan losses [Roll Forward]
Beginning balance	44,187	46,350
Provision for loan losses	(1,375)	(2,000)
Loans charged off	0	0
Recoveries	0	0
Ending balance	42,812	44,350
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	0	0
Provision for off-balance sheet credit losses	0	0
Ending balance	0	0
Total provision for credit losses	$ (1,375)	$ (2,000)