Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Segment Income Statement Data
Net interest income	$ 154,267	$ 154,123	$ 308,935	$ 307,846
Noninterest income	75,951	61,586	154,397	132,591
Total revenue	230,218	215,709	463,332	440,437
Credit provision	0	16,000	0	47,000
Noninterest expense	166,030	155,717	335,792	318,716
Income (loss) before income taxes	64,188	43,992	127,540	74,721
Income tax expense (benefit)	20,871	9,610	41,590	17,486
Net income (loss)	43,317	34,382	85,950	57,235
Return on average allocated capital	9.30%	6.08%	9.20%	4.93%
Segment Balance Sheet Data
Average earning assets	19,386,046	19,431,292	19,378,888	19,364,948
Average loans	14,602,602	13,004,904	14,456,522	12,840,289
Average deposits	15,050,684	14,052,689	15,025,625	14,148,618
Average allocated capital	1,825,441	1,688,230	1,812,684	1,677,084
Commercial Banking [Member]
Segment Income Statement Data
Net interest income	69,260	63,060	139,348	127,003
Noninterest income	19,267	20,889	38,548	43,914
Total revenue	88,527	83,949	177,896	170,917
Credit provision	11,431	9,898	22,318	19,635
Noninterest expense	52,617	47,225	106,361	95,246
Income (loss) before income taxes	24,479	26,826	49,217	56,036
Income tax expense (benefit)	8,568	9,389	17,226	19,613
Net income (loss)	15,911	17,437	31,991	36,423
Return on average allocated capital	8.36%	9.62%	8.54%	10.04%
Segment Balance Sheet Data
Average earning assets	7,379,242	6,236,243	7,228,587	6,142,152
Average loans	7,373,456	6,231,238	7,224,167	6,138,171
Average deposits	4,279,033	3,170,140	4,324,892	3,281,432
Average allocated capital	765,670	727,270	753,140	731,382
Consumer Banking [Member]
Segment Income Statement Data
Net interest income	77,423	83,445	157,776	167,198
Noninterest income	54,107	40,102	107,559	83,788
Total revenue	131,530	123,547	265,335	250,986
Credit provision	4,848	4,430	9,775	8,780
Noninterest expense	106,110	107,945	212,803	216,684
Income (loss) before income taxes	20,572	11,172	42,757	25,522
Income tax expense (benefit)	7,200	3,910	14,965	8,932
Net income (loss)	13,372	7,262	27,792	16,590
Return on average allocated capital	9.18%	5.39%	9.48%	6.22%
Segment Balance Sheet Data
Average earning assets	7,194,285	6,749,142	7,205,121	6,683,176
Average loans	7,194,285	6,749,142	7,205,121	6,683,176
Average deposits	9,449,124	9,583,298	9,431,508	9,511,089
Average allocated capital	585,984	540,814	589,417	538,070
Risk Management and Shared Services [Member]
Segment Income Statement Data
Net interest income	7,584	7,618	11,811	13,645
Noninterest income	2,577	595	8,290	4,889
Total revenue	10,161	8,213	20,101	18,534
Credit provision	(16,279)	1,672	(32,093)	18,585
Noninterest expense	7,303	547	16,628	6,786
Income (loss) before income taxes	19,137	5,994	35,566	(6,837)
Income tax expense (benefit)	5,103	(3,689)	9,399	(11,059)
Net income (loss)	14,034	9,683	26,167	4,222
Return on average allocated capital	10.80%	0.83%	10.10%	(5.94%)
Segment Balance Sheet Data
Average earning assets	4,812,519	6,445,907	4,945,180	6,539,620
Average loans	34,861	24,524	27,234	18,942
Average deposits	1,322,527	1,299,251	1,269,225	1,356,097
Average allocated capital	$ 473,787	$ 420,146	$ 470,127	$ 407,632