Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
OPERATIONS:
Net interest income	$ 186,078	$ 185,118	$ 371,234	$ 370,741
Provision/ (recapture) for loan losses	6,391	8,966	14,200	17,214
Noninterest Income	65,115	66,582	132,509	132,429
Other expenses	160,320	161,674	327,283	322,326
Net income	58,309	56,584	112,445	113,723
AVERAGES :
Assets	25,923,566	25,129,859	25,846,647	25,015,734
Loans	16,242,902	15,577,361	16,161,173	15,502,686
Earning assets	23,121,303	22,352,721	23,005,692	22,227,267
Deposits	20,967,450	19,682,662	20,801,559	19,735,499
Economic capital	3,012,218	2,892,432	2,991,190	2,879,469
Other
OPERATIONS:
Net interest income	(15,918)	(14,177)	(34,661)	(27,548)
Provision/ (recapture) for loan losses	218	(1,765)	(1,636)	(355)
Noninterest Income	7,125	5,884	15,438	13,528
Other expenses	4,356	(618)	8,251	(3,610)
Net income	(5,293)	54	(9,818)	828
AVERAGES :
Assets	9,638,361	9,449,572	9,639,033	9,374,463
Loans	41,656	60,490	46,706	59,274
Earning assets	6,555,458	6,535,441	6,523,236	6,483,544
Deposits	1,410,044	610,711	1,111,129	573,990
Economic capital	770,591	657,810	742,055	656,765
Commercial Loan | Operating Segments
OPERATIONS:
Net interest income	101,313	101,342	203,932	202,830
Provision/ (recapture) for loan losses	1,070	2,285	6,842	1,759
Noninterest Income	20,782	21,918	41,961	44,408
Other expenses	57,201	61,032	118,221	122,685
Net income	41,486	38,963	78,539	79,816
AVERAGES :
Assets	9,600,103	9,437,824	9,596,152	9,445,975
Loans	9,721,866	9,533,843	9,715,827	9,520,262
Earning assets	10,081,198	9,828,867	10,077,716	9,811,770
Deposits	7,269,121	6,777,434	7,373,805	6,831,887
Economic capital	1,251,845	1,355,049	1,252,069	1,349,289
Retail | Operating Segments
OPERATIONS:
Net interest income	94,369	92,501	189,096	184,527
Provision/ (recapture) for loan losses	5,123	8,447	9,169	15,981
Noninterest Income	22,079	23,964	45,673	45,701
Other expenses	84,880	87,799	173,575	176,070
Net income	17,189	13,142	33,816	24,815
AVERAGES :
Assets	6,370,350	5,951,665	6,301,303	5,898,835
Loans	6,173,352	5,702,015	6,097,054	5,636,666
Earning assets	6,178,619	5,707,400	6,103,154	5,645,469
Deposits	11,003,769	11,105,954	11,014,512	11,115,005
Economic capital	867,958	767,803	870,360	763,446
Wealth | Operating Segments
OPERATIONS:
Net interest income	6,314	5,452	12,867	10,932
Provision/ (recapture) for loan losses	(20)	(1)	(175)	(171)
Noninterest Income	15,129	14,816	29,437	28,792
Other expenses	13,883	13,461	27,236	27,181
Net income	4,927	4,425	9,908	8,264
AVERAGES :
Assets	314,752	290,798	310,159	296,461
Loans	306,028	281,013	301,586	286,484
Earning assets	306,028	281,013	301,586	286,484
Deposits	1,284,516	1,188,563	1,302,113	1,214,617
Economic capital	$ 121,824	$ 111,770	$ 126,706	$ 109,969