Loans and Allowances for Credit Losses Part 2 (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Allowance for loan losses [Roll Forward]
Beginning balance	$ 205,965	$ 244,209	$ 215,507	$ 253,481
Provision for loan losses	(499)	(7,699)	(7,689)	(8,486)
Loans charged off	(8,552)	(11,543)	(17,461)	(25,217)
Recoveries	6,210	6,702	12,767	11,891
Ending balance	203,124	231,669	203,124	231,669
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	1,105	10,048	1,915	9,261
Provision for off-balance sheet credit losses	499	(301)	(311)	486
Ending balance	1,604	9,747	1,604	9,747
Total provision for credit losses	0	(8,000)	(8,000)	(8,000)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	12,318,732	11,431,948	12,318,732	11,431,948	12,177,046
Individually measured for impairment, recorded investment	122,050	144,483	122,050	144,483	134,410
Total	12,440,782	11,576,431	12,440,782	11,576,431	12,311,456
Related allowance [Abstract]
Collectively measured for impairment, related allowance	158,631	188,976	158,631	188,976	167,087
Individually measured for impairment, related allowance	2,044	1,835	2,044	1,835	4,233
Total measured for impairment, related allowance	203,124	231,669	203,124	231,669
Commercial [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	66,419	85,972	65,280	83,443
Provision for loan losses	223	(2,526)	(1,733)	991
Loans charged off	(4,538)	(4,094)	(4,836)	(7,028)
Recoveries	1,940	4,125	5,333	6,071
Ending balance	64,044	83,477	64,044	83,477
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	405	8,362	475	7,906
Provision for off-balance sheet credit losses	(3)	(138)	(73)	318
Ending balance	402	8,224	402	8,224
Total provision for credit losses	220	(2,664)	(1,806)	1,309
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	7,687,251	7,001,006	7,687,251	7,001,006	7,617,445
Individually measured for impairment, recorded investment	20,869	34,529	20,869	34,529	24,467
Total	7,708,120	7,035,535	7,708,120	7,035,535	7,641,912
Related allowance [Abstract]
Collectively measured for impairment, related allowance	63,492	83,199	63,492	83,199	65,050
Individually measured for impairment, related allowance	552	278	552	278	230
Total measured for impairment, related allowance	64,044	83,477	64,044	83,477
Commercial Real Estate [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	48,528	62,742	54,884	67,034
Provision for loan losses	(1,118)	(6,264)	(3,798)	(5,143)
Loans charged off	(450)	(1,216)	(5,250)	(7,941)
Recoveries	2,727	544	3,851	1,856
Ending balance	49,687	55,806	49,687	55,806
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	618	1,575	1,353	1,250
Provision for off-balance sheet credit losses	560	(150)	(175)	175
Ending balance	1,178	1,425	1,178	1,425
Total provision for credit losses	(558)	(6,414)	(3,973)	(4,968)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	2,258,403	2,069,516	2,258,403	2,069,516	2,168,373
Individually measured for impairment, recorded investment	58,693	80,214	58,693	80,214	60,626
Total	2,317,096	2,149,730	2,317,096	2,149,730	2,228,999
Related allowance [Abstract]
Collectively measured for impairment, related allowance	48,493	54,526	48,493	54,526	51,775
Individually measured for impairment, related allowance	1,194	1,280	1,194	1,280	3,109
Total measured for impairment, related allowance	49,687	55,806	49,687	55,806
Residential Mortgage [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	40,222	41,628	41,703	46,476
Provision for loan losses	597	4,371	323	898
Loans charged off	(2,057)	(4,061)	(3,836)	(5,847)
Recoveries	444	750	1,016	1,161
Ending balance	39,206	42,688	39,206	42,688
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	72	82	78	91
Provision for off-balance sheet credit losses	(66)	(2)	(72)	(11)
Ending balance	6	80	6	80
Total provision for credit losses	531	4,369	251	887
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	1,999,334	1,980,158	1,999,334	1,980,158	1,998,432
Individually measured for impairment, recorded investment	40,451	22,727	40,451	22,727	46,608
Total	2,039,785	2,002,885	2,039,785	2,002,885	2,045,040
Related allowance [Abstract]
Collectively measured for impairment, related allowance	39,028	42,453	39,028	42,453	40,934
Individually measured for impairment, related allowance	178	235	178	235	769
Total measured for impairment, related allowance	39,206	42,688	39,206	42,688
Consumer [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	7,984	9,517	9,453	10,178
Provision for loan losses	162	212	(743)	260
Loans charged off	(1,507)	(2,172)	(3,539)	(4,401)
Recoveries	1,099	1,283	2,567	2,803
Ending balance	7,738	8,840	7,738	8,840
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	10	29	9	14
Provision for off-balance sheet credit losses	8	(11)	9	4
Ending balance	18	18	18	18
Total provision for credit losses	170	201	(734)	264
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	373,744	381,268	373,744	381,268	392,796
Individually measured for impairment, recorded investment	2,037	7,013	2,037	7,013	2,709
Total	375,781	388,281	375,781	388,281	395,505
Related allowance [Abstract]
Collectively measured for impairment, related allowance	7,618	8,798	7,618	8,798	9,328
Individually measured for impairment, related allowance	120	42	120	42	125
Total measured for impairment, related allowance	7,738	8,840	7,738	8,840
Total Portfolio Segment Allocation [Member]
Allowance for loan losses [Roll Forward]
Beginning balance					171,320
Ending balance	160,675	190,811	160,675	190,811	171,320
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	12,318,732	11,431,948	12,318,732	11,431,948	12,177,046
Individually measured for impairment, recorded investment	122,050	144,483	122,050	144,483	134,410
Total	12,440,782	11,576,431	12,440,782	11,576,431	12,311,456
Related allowance [Abstract]
Collectively measured for impairment, related allowance	158,631	188,976	158,631	188,976	167,087
Individually measured for impairment, related allowance	2,044	1,835	2,044	1,835	4,233
Total measured for impairment, related allowance	160,675	190,811	160,675	190,811	171,320
Nonspecific allowance [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	42,812	44,350	44,187	46,350
Provision for loan losses	(363)	(3,492)	(1,738)	(5,492)
Loans charged off	0	0	0	0
Recoveries	0	0	0	0
Ending balance	42,449	40,858	42,449	40,858
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	0	0	0	0
Provision for off-balance sheet credit losses	0	0	0	0
Ending balance	0	0	0	0
Total provision for credit losses	(363)	(3,492)	(1,738)	(5,492)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	0	0	0	0	0
Individually measured for impairment, recorded investment	0	0	0	0	0
Total	0	0	0	0	0
Related allowance [Abstract]
Collectively measured for impairment, related allowance	0	0	0	0	0
Individually measured for impairment, related allowance	0	0	0	0	0
Total measured for impairment, related allowance	$ 42,449	$ 40,858	$ 42,449	$ 40,858