Segment Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
OPERATIONS:
Net interest income	$ 741,295	$ 775,568	$ 710,785
Provision for loan losses	45,100	52,279	33,684
Other income	268,998	281,524	270,343
Other expenses	638,690	664,919	684,253
Net income	229,484	237,951	183,684
AVERAGES :
Assets	25,155,792	24,418,211	21,489,775
Loans	15,673,200	14,891,315	12,948,666
Earnings assets	22,439,516	21,502,747	18,492,995
Deposits	19,858,850	19,528,435	17,301,588
Economic Capital	2,903,160	2,790,139	2,408,865
Commercial Loan
OPERATIONS:
Net interest income	406,520	417,788	408,006
Provision for loan losses	16,373	2,898	17,072
Other income	88,384	91,483	83,933
Other expenses	240,634	247,258	209,936
Net income	154,632	171,560	172,206
AVERAGES :
Assets	9,464,876	9,265,088	8,397,357
Loans	9,550,421	9,262,224	8,292,805
Earnings assets	9,868,378	9,549,341	8,480,005
Deposits	7,071,238	6,679,007	5,572,287
Economic Capital	1,309,589	1,318,357	602,561
Retail
OPERATIONS:
Net interest income	370,781	383,151	349,433
Provision for loan losses	28,152	39,618	16,151
Other income	96,979	106,716	114,679
Other expenses	345,827	359,848	330,875
Net income	60,957	58,760	76,105
AVERAGES :
Assets	6,022,529	5,641,517	4,746,277
Loans	5,775,543	5,305,071	4,367,701
Earnings assets	5,783,272	5,328,107	4,392,937
Deposits	11,035,639	11,484,763	10,749,725
Economic Capital	807,150	741,165	256,362
Wealth
OPERATIONS:
Net interest income	22,403	20,330	17,192
Provision for loan losses	94	1,895	(692)
Other income	57,995	55,800	48,289
Other expenses	54,681	54,204	54,196
Net income	16,654	13,021	7,784
AVERAGES :
Assets	298,435	271,975	259,601
Loans	289,044	261,321	226,152
Earnings assets	289,044	261,321	226,179
Deposits	1,215,174	1,089,068	826,794
Economic Capital	115,447	100,327	72,244
Other
OPERATIONS:
Net interest income	(58,409)	(45,701)	(63,846)
Provision for loan losses	481	7,868	1,153
Other income	25,640	27,525	23,442
Other expenses	(2,452)	3,609	89,246
Net income	(2,759)	(5,390)	(72,411)
AVERAGES :
Assets	9,369,952	9,239,631	8,086,540
Loans	58,192	62,699	62,008
Earnings assets	6,498,822	6,363,978	5,393,874
Deposits	536,799	275,597	152,782
Economic Capital	$ 670,974	$ 630,290	$ 1,477,698