Loans and Allowances for Credit Losses Part 2 (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Allowance for loan losses [Roll Forward]
Beginning balance	$ 188,318,000	$ 205,965,000	$ 185,396,000	$ 215,507,000
Provision for loan losses	370,000	(499,000)	780,000	(7,689,000)
Loans charged off	(3,522,000)	(8,552,000)	(6,370,000)	(17,461,000)
Recoveries	5,524,000	6,210,000	10,884,000	12,767,000
Ending balance	190,690,000	203,124,000	190,690,000	203,124,000
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	1,678,000	1,105,000	2,088,000	1,915,000
Provision for off-balance sheet credit losses	(370,000)	499,000	(780,000)	(311,000)
Ending balance	1,308,000	1,604,000	1,308,000	1,604,000
Total provision for credit losses	0	0	0	(8,000,000)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	13,330,178,000	12,318,732,000	13,330,178,000	12,318,732,000	12,691,892,000
Individually measured for impairment, recorded investment	96,680,000	122,050,000	96,680,000	122,050,000	100,372,000
Total	13,426,858,000	12,440,782,000	13,426,858,000	12,440,782,000	12,792,264,000
Related allowance [Abstract]
Collectively measured for impairment, related allowance	160,308,000	158,631,000	160,308,000	158,631,000	156,229,000
Individually measured for impairment, related allowance	3,433,000	2,044,000	3,433,000	2,044,000	954,000
Total measured for impairment, related allowance	190,690,000	203,124,000	190,690,000	203,124,000
Commercial [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	85,246,000	66,419,000	79,180,000	65,280,000
Provision for loan losses	1,393,000	223,000	5,618,000	(1,733,000)
Loans charged off	(29,000)	(4,538,000)	(173,000)	(4,836,000)
Recoveries	1,196,000	1,940,000	3,181,000	5,333,000
Ending balance	87,806,000	64,044,000	87,806,000	64,044,000
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	576,000	405,000	119,000	475,000
Provision for off-balance sheet credit losses	(231,000)	(3,000)	226,000	(73,000)
Ending balance	345,000	402,000	345,000	402,000
Total provision for credit losses	1,162,000	220,000	5,844,000	(1,806,000)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	8,350,558,000	7,687,251,000	8,350,558,000	7,687,251,000	7,926,461,000
Individually measured for impairment, recorded investment	17,103,000	20,869,000	17,103,000	20,869,000	16,760,000
Total	8,367,661,000	7,708,120,000	8,367,661,000	7,708,120,000	7,943,221,000
Related allowance [Abstract]
Collectively measured for impairment, related allowance	84,639,000	63,492,000	84,639,000	63,492,000	78,607,000
Individually measured for impairment, related allowance	3,167,000	552,000	3,167,000	552,000	573,000
Total measured for impairment, related allowance	87,806,000	64,044,000	87,806,000	64,044,000
Commercial Real Estate [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	41,589,000	48,528,000	41,573,000	54,884,000
Provision for loan losses	(2,958,000)	(1,118,000)	(4,549,000)	(3,798,000)
Loans charged off	0	(450,000)	(220,000)	(5,250,000)
Recoveries	2,621,000	2,727,000	4,448,000	3,851,000
Ending balance	41,252,000	49,687,000	41,252,000	49,687,000
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	1,040,000	618,000	1,876,000	1,353,000
Provision for off-balance sheet credit losses	(138,000)	560,000	(974,000)	(175,000)
Ending balance	902,000	1,178,000	902,000	1,178,000
Total provision for credit losses	(3,096,000)	(558,000)	(5,523,000)	(3,973,000)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	2,620,506,000	2,258,403,000	2,620,506,000	2,258,403,000	2,374,503,000
Individually measured for impairment, recorded investment	34,472,000	58,693,000	34,472,000	58,693,000	40,850,000
Total	2,654,978,000	2,317,096,000	2,654,978,000	2,317,096,000	2,415,353,000
Related allowance [Abstract]
Collectively measured for impairment, related allowance	41,069,000	48,493,000	41,069,000	48,493,000	41,440,000
Individually measured for impairment, related allowance	183,000	1,194,000	183,000	1,194,000	133,000
Total measured for impairment, related allowance	41,252,000	49,687,000	41,252,000	49,687,000
Residential Mortgage [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	28,307,000	40,222,000	29,465,000	41,703,000
Provision for loan losses	467,000	597,000	(49,000)	323,000
Loans charged off	(1,842,000)	(2,057,000)	(2,838,000)	(3,836,000)
Recoveries	722,000	444,000	1,076,000	1,016,000
Ending balance	27,654,000	39,206,000	27,654,000	39,206,000
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	62,000	72,000	90,000	78,000
Provision for off-balance sheet credit losses	(19,000)	(66,000)	(47,000)	(72,000)
Ending balance	43,000	6,000	43,000	6,000
Total provision for credit losses	448,000	531,000	(96,000)	251,000
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	1,963,875,000	1,999,334,000	1,963,875,000	1,999,334,000	2,010,483,000
Individually measured for impairment, recorded investment	44,340,000	40,451,000	44,340,000	40,451,000	41,543,000
Total	2,008,215,000	2,039,785,000	2,008,215,000	2,039,785,000	2,052,026,000
Related allowance [Abstract]
Collectively measured for impairment, related allowance	27,571,000	39,028,000	27,571,000	39,028,000	29,217,000
Individually measured for impairment, related allowance	83,000	178,000	83,000	178,000	248,000
Total measured for impairment, related allowance	27,654,000	39,206,000	27,654,000	39,206,000
Consumer [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	6,211,000	7,984,000	6,965,000	9,453,000
Provision for loan losses	1,484,000	162,000	1,024,000	(743,000)
Loans charged off	(1,651,000)	(1,507,000)	(3,139,000)	(3,539,000)
Recoveries	985,000	1,099,000	2,179,000	2,567,000
Ending balance	7,029,000	7,738,000	7,029,000	7,738,000
Allowance for off-balance sheet credit losses [Roll Forward]
Beginning balance	0	10,000	3,000	9,000
Provision for off-balance sheet credit losses	18,000	8,000	15,000	9,000
Ending balance	18,000	18,000	18,000	18,000
Total provision for credit losses	1,502,000	170,000	1,039,000	(734,000)
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	395,239,000	373,744,000	395,239,000	373,744,000	380,445,000
Individually measured for impairment, recorded investment	765,000	2,037,000	765,000	2,037,000	1,219,000
Total	396,004,000	375,781,000	396,004,000	375,781,000	381,664,000
Related allowance [Abstract]
Collectively measured for impairment, related allowance	7,029,000	7,618,000	7,029,000	7,618,000	6,965,000
Individually measured for impairment, related allowance	0	120,000	0	120,000	0
Total measured for impairment, related allowance	7,029,000	7,738,000	7,029,000	7,738,000
Specific Allowance [Member]
Allowance for loan losses [Roll Forward]
Beginning balance					157,183,000
Ending balance	163,741,000	160,675,000	163,741,000	160,675,000	157,183,000
Recorded investment [Abstract]
Collectively measured for impairment, recorded investment	13,330,178,000	12,318,732,000	13,330,178,000	12,318,732,000	12,691,892,000
Individually measured for impairment, recorded investment	96,680,000	122,050,000	96,680,000	122,050,000	100,372,000
Total	13,426,858,000	12,440,782,000	13,426,858,000	12,440,782,000	12,792,264,000
Related allowance [Abstract]
Collectively measured for impairment, related allowance	160,308,000	158,631,000	160,308,000	158,631,000	156,229,000
Individually measured for impairment, related allowance	3,433,000	2,044,000	3,433,000	2,044,000	954,000
Total measured for impairment, related allowance	163,741,000	160,675,000	163,741,000	160,675,000	157,183,000
Nonspecific Allowance [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	26,965,000	42,812,000	28,213,000	44,187,000
Provision for loan losses	(16,000)	(363,000)	(1,264,000)	(1,738,000)
Loans charged off	0	0	0	0
Recoveries	0	0	0	0
Ending balance	26,949,000	42,449,000	26,949,000	42,449,000
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	(16,000)	(363,000)	(1,264,000)	(1,738,000)
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	$ 26,949,000	$ 42,449,000	$ 26,949,000	$ 42,449,000