Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Income Statement Data Abstract
Net interest income	$ 645,543	$ 625,992	$ 612,831
Noninterest income	313,099	313,290	273,119
Total revenue	958,642	939,282	885,950
Credit provision	10,000	3,000	52,000
Noninterest expense	680,749	681,823	650,523
Income before income taxes	267,893	254,459	183,427
Income tax expense (benefit)	79,201	75,486	43,728
Net income	188,692	178,973	139,699
Return on average allocated capital	9.80%	9.50%	6.70%
Segment Balance Sheet Data
Average earning assets	20,980,128	19,613,777	19,442,263
Average loans	15,663,145	14,741,785	13,278,848
Average deposits	17,438,195	15,582,369	14,401,127
Average allocated capital	1,878,371	1,838,424	1,713,155
Commercial Banking Segment [Member]
Segment Income Statement Data Abstract
Net interest income	318,377	290,594	264,728
Noninterest income	94,450	86,912	86,087
Total revenue	412,827	377,506	350,815
Credit provision	55,198	46,563	40,259
Noninterest expense	187,277	194,327	191,038
Income before income taxes	170,352	136,616	119,518
Income tax expense (benefit)	59,623	47,816	41,831
Net income	110,729	88,800	77,687
Return on average allocated capital	14.20%	12.10%	11.00%
Segment Balance Sheet Data
Average earning assets	8,443,203	7,540,502	6,498,071
Average loans	8,433,389	7,534,026	6,494,133
Average deposits	5,479,567	4,613,215	3,685,191
Average allocated capital	778,098	731,943	705,775
Consumer Banking Segment [Member]
Segment Income Statement Data Abstract
Net interest income	317,016	301,807	317,020
Noninterest income	201,634	207,234	176,236
Total revenue	518,650	509,041	493,256
Credit provision	20,122	19,419	17,988
Noninterest expense	428,591	440,611	441,468
Income before income taxes	69,937	49,011	33,800
Income tax expense (benefit)	24,478	17,154	11,830
Net income	45,459	31,857	21,970
Return on average allocated capital	8.50%	5.70%	4.20%
Segment Balance Sheet Data
Average earning assets	7,225,943	7,182,766	6,653,451
Average loans	7,225,943	7,182,766	6,653,451
Average deposits	9,675,302	9,441,330	9,446,488
Average allocated capital	535,783	562,125	523,168
Other Segment [Member]
Segment Income Statement Data Abstract
Net interest income	10,150	33,591	31,083
Noninterest income	17,015	19,144	10,796
Total revenue	27,165	52,735	41,879
Credit provision	(65,320)	(62,982)	(6,247)
Noninterest expense	64,881	46,885	18,017
Income before income taxes	27,604	68,832	30,109
Income tax expense (benefit)	(4,900)	10,516	(9,933)
Net income	32,504	58,316	40,042
Return on average allocated capital	4.80%	9.80%	3.10%
Segment Balance Sheet Data
Average earning assets	5,310,982	4,890,509	6,290,741
Average loans	3,813	24,993	131,264
Average deposits	2,283,326	1,527,824	1,269,448
Average allocated capital	$ 564,490	$ 544,356	$ 484,212