Fair Value Measurement (Recurring and Nonrecurring Table) (Details) (USD $)	3 Months Ended				12 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
True-up Liabitlity Discount Rate	3.05%		3.46%
True-up Liability Effect of Change in Discount Rate By One Percent	$ 700,000		$ (700,000)
Collateral Dependant Impaired and Non Accrual Loans Carrying Amount	63,800,000		58,300,000		56,000,000
Recurring Fair Value Measurements
Available-for-sale	3,791,059,000		3,433,171,000		3,545,288,000
Residential loans held for sale	3,568,000		7,143,000		13,428,000
Derivative Asset, Fair Value, Gross Asset	72,573,000		46,467,000		55,197,000
Total Assets, Fair Value Disclosure, Recurring	3,867,200,000		3,486,781,000		3,613,913,000
Derivative Liability, Fair Value, Gross Liability	65,447,000		55,106,000		55,439,000
True Up Liability	13,707,000		11,983,000		13,294,000
Total liabilities at fair value on a recurring basis	79,154,000	[1]	67,089,000		68,733,000	[1]
Nonrecurring Fair Value Measurements [Abstract]
Fair Value of Mortgage Servicing Rights	20,526,000	[2]	22,631,000		21,228,000	[2]
Impaired and Non Accrual Loans Fair Value Disclosure	63,839,000	[3]	58,296,000		56,041,000	[3]
Other Real Estate, Non Covered	16,956,000	[4]	11,568,000		12,510,000	[4]
Other Real Estate Covered by Loss Share	7,293,000	[5]	19,708,000		3,614,000	[5]
Nonrecurring Fair Value	108,614,000		112,203,000		93,393,000
Impairment of Noncovered Other Real Estate Owned	900,000		800,000		2,600,000
Impairment of Covered Other Real Esate Owned	100,000		400,000		1,200,000
Level 1
Recurring Fair Value Measurements
Available-for-sale	2,869,000		3,055,000		2,974,000
Residential loans held for sale	0		0		0
Derivative Asset, Fair Value, Gross Asset	0		0		0
Total Assets, Fair Value Disclosure, Recurring	2,869,000		3,055,000		2,974,000
Derivative Liability, Fair Value, Gross Liability	0		0		0
True Up Liability	0		0		0
Total liabilities at fair value on a recurring basis	0	[1]	0		0	[1]
Nonrecurring Fair Value Measurements [Abstract]
Fair Value of Mortgage Servicing Rights	0	[2]	0		0	[2]
Impaired and Non Accrual Loans Fair Value Disclosure	0	[3]	0		0	[3]
Other Real Estate, Non Covered	0	[4]	0		0	[4]
Other Real Estate Covered by Loss Share	0	[5]	0		0	[5]
Nonrecurring Fair Value	0		0		0
Level 2
Recurring Fair Value Measurements
Available-for-sale	3,441,959,000		3,080,691,000		3,203,127,000
Residential loans held for sale	3,568,000		7,143,000		13,428,000
Derivative Asset, Fair Value, Gross Asset	72,573,000		46,467,000		55,197,000
Total Assets, Fair Value Disclosure, Recurring	3,518,100,000		3,134,301,000		3,271,752,000
Derivative Liability, Fair Value, Gross Liability	65,447,000		55,106,000		55,439,000
True Up Liability	0		0		0
Total liabilities at fair value on a recurring basis	65,447,000	[1]	55,106,000		55,439,000	[1]
Nonrecurring Fair Value Measurements [Abstract]
Fair Value of Mortgage Servicing Rights	0	[2]	0		0	[2]
Impaired and Non Accrual Loans Fair Value Disclosure	0	[3]	0		0	[3]
Other Real Estate, Non Covered	0	[4]	0		0	[4]
Other Real Estate Covered by Loss Share	0	[5]	0		0	[5]
Nonrecurring Fair Value	0		0		0
Level 3
Recurring Fair Value Measurements
Available-for-sale	346,231,000		349,425,000		339,187,000
Residential loans held for sale	0		0		0
Derivative Asset, Fair Value, Gross Asset	0		0		0
Total Assets, Fair Value Disclosure, Recurring	346,231,000		349,425,000		339,187,000
Derivative Liability, Fair Value, Gross Liability	0		0		0
True Up Liability	13,707,000		11,983,000		13,294,000
Total liabilities at fair value on a recurring basis	13,707,000	[1]	11,983,000		13,294,000	[1]
Nonrecurring Fair Value Measurements [Abstract]
Fair Value of Mortgage Servicing Rights	20,526,000		22,631,000		21,228,000
Impaired and Non Accrual Loans Fair Value Disclosure	63,839,000		58,296,000		56,041,000
Other Real Estate, Non Covered	16,956,000		11,568,000		12,510,000	[4]
Other Real Estate Covered by Loss Share	7,293,000		19,708,000		3,614,000	[5]
Nonrecurring Fair Value	108,614,000		112,203,000		93,393,000
US Treasury Securities
Recurring Fair Value Measurements
Available-for-sale	0
Equity Securities
Recurring Fair Value Measurements
Available-for-sale	2,869,000		3,055,000		2,974,000
Equity Securities | Level 1
Recurring Fair Value Measurements
Available-for-sale	2,869,000		3,055,000		2,974,000
Equity Securities | Level 2
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Equity Securities | Level 3
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Non-marketable Equity Securities
Recurring Fair Value Measurements
Available-for-sale			3,281,000
Non-marketable Equity Securities | Level 2
Recurring Fair Value Measurements
Available-for-sale			10,000
Non-marketable Equity Securities | Level 3
Recurring Fair Value Measurements
Available-for-sale			3,271,000
US Government Agencies Debt Securities
Recurring Fair Value Measurements
Available-for-sale	2,513,000				2,482,000
U.S. States and political subdivisions debt securities
Recurring Fair Value Measurements
Available-for-sale	215,164,000		250,980,000		227,342,000
U.S. States and political subdivisions debt securities | Level 1
Recurring Fair Value Measurements
Available-for-sale	0		0		0
U.S. States and political subdivisions debt securities | Level 2
Recurring Fair Value Measurements
Available-for-sale	215,164,000		250,980,000		227,342,000
U.S. States and political subdivisions debt securities | Level 3
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	947,303,000		1,023,994,000		970,998,000
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises | Level 1
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises | Level 2
Recurring Fair Value Measurements
Available-for-sale			1,023,994,000		970,998,000
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises | Level 3
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	140,359,000		85,133,000		103,403,000
Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises | Level 1
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises | Level 2
Recurring Fair Value Measurements
Available-for-sale			85,133,000		103,403,000
Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises | Level 3
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	1,892,560,000		1,548,104,000		1,676,567,000
Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises | Level 1
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises | Level 2
Recurring Fair Value Measurements
Available-for-sale			1,548,104,000		1,676,567,000
Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises | Level 3
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency
Recurring Fair Value Measurements
Available-for-sale	6,000		8,000		7,000
Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency | Level 1
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency | Level 2
Recurring Fair Value Measurements
Available-for-sale	1,000		1,000		1,000
Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency | Level 3
Recurring Fair Value Measurements
Available-for-sale	5,000		7,000		6,000
Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	244,059,000		172,469,000		222,334,000
Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises | Level 1
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises | Level 2
Recurring Fair Value Measurements
Available-for-sale			172,469,000		222,334,000
Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises | Level 3
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Corporate debt securities
Recurring Fair Value Measurements
Available-for-sale	52,264,000		51,588,000		51,337,000
Corporate debt securities | Level 1
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Corporate debt securities | Level 2
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Corporate debt securities | Level 3
Recurring Fair Value Measurements
Available-for-sale			51,588,000		51,337,000
Collateralized Loan Obligations
Recurring Fair Value Measurements
Available-for-sale	293,962,000		294,559,000		287,844,000
Collateralized Loan Obligations | Level 1
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Collateralized Loan Obligations | Level 2
Recurring Fair Value Measurements
Available-for-sale	0		0		0
Collateralized Loan Obligations | Level 3
Recurring Fair Value Measurements
Available-for-sale			294,559,000		287,844,000
Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	59,885,000	[6]	46,466,000	[6]	49,941,000	[6]
Derivative Liability, Fair Value, Gross Liability	59,384,000		44,714,000		48,756,000
Credit Risk Contract | Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0	[6]	0	[6]	0	[6]
Derivative Liability, Fair Value, Gross Liability	0		0		0
Interest Rate Swap | Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	12,688,000		1,000	[6]	5,256,000	[6]
Derivative Liability, Fair Value, Gross Liability	6,063,000		10,392,000		6,683,000
Interest Rate Swap | Designated as Hedging Instrument | Level 1
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0		0		0
Derivative Liability, Fair Value, Gross Liability	0		0		0
Interest Rate Swap | Designated as Hedging Instrument | Level 2
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	12,688,000		1,000		5,256,000
Derivative Liability, Fair Value, Gross Liability	6,063,000		10,392,000		6,683,000
Interest Rate Swap | Designated as Hedging Instrument | Level 3
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0		0		0
Derivative Liability, Fair Value, Gross Liability	0		0		0
Interest Rate Swap | Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	59,147,000		44,672,000	[6]	48,366,000	[6]
Derivative Liability, Fair Value, Gross Liability	59,147,000		44,672,000		48,366,000
Interest Rate Swap | Not Designated as Hedging Instrument | Level 1
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0		0		0
Derivative Liability, Fair Value, Gross Liability	0		0		0
Interest Rate Swap | Not Designated as Hedging Instrument | Level 2
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	59,147,000		44,672,000		48,366,000
Derivative Liability, Fair Value, Gross Liability	59,147,000		44,672,000		48,366,000
Interest Rate Swap | Not Designated as Hedging Instrument | Level 3
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0		0		0
Derivative Liability, Fair Value, Gross Liability	0		0		0
Mortgage Loan Commitments | Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	388,000		1,575,000	[6]	1,408,000	[6]
Derivative Liability, Fair Value, Gross Liability	0		0		0
Mortgage Loan Commitments | Not Designated as Hedging Instrument | Level 1
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0		0		0
Mortgage Loan Commitments | Not Designated as Hedging Instrument | Level 2
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	388,000		1,575,000		1,408,000
Mortgage Loan Commitments | Not Designated as Hedging Instrument | Level 3
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0		0		0
Forward sales contracts | Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset			167,000	[6]	0	[6]
Derivative Liability, Fair Value, Gross Liability	68,000		0		272,000
Forward sales contracts | Not Designated as Hedging Instrument | Level 1
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset			0		0
Derivative Liability, Fair Value, Gross Liability	0				0
Forward sales contracts | Not Designated as Hedging Instrument | Level 2
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0		167,000		0
Derivative Liability, Fair Value, Gross Liability	68,000				272,000
Forward sales contracts | Not Designated as Hedging Instrument | Level 3
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset			0		0
Derivative Liability, Fair Value, Gross Liability	0				0
Foreign Exchange | Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	350,000		52,000	[6]	167,000	[6]
Derivative Liability, Fair Value, Gross Liability	169,000		42,000		118,000
Foreign Exchange | Not Designated as Hedging Instrument | Level 1
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0		0		0
Derivative Liability, Fair Value, Gross Liability	0		0		0
Foreign Exchange | Not Designated as Hedging Instrument | Level 2
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	350,000		52,000		167,000
Derivative Liability, Fair Value, Gross Liability	169,000		42,000		118,000
Foreign Exchange | Not Designated as Hedging Instrument | Level 3
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0		0		0
Derivative Liability, Fair Value, Gross Liability	0		0		0
Other Contract | Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	0		0	[6]	0	[6]
Derivative Liability, Fair Value, Gross Liability	0		0		0
Other Contract | Not Designated as Hedging Instrument | Level 1
Recurring Fair Value Measurements
Derivative Liability, Fair Value, Gross Liability	0
Other Contract | Not Designated as Hedging Instrument | Level 3
Recurring Fair Value Measurements
Derivative Liability, Fair Value, Gross Liability	$ 0

[1] (1) There were no transfers between levels 1, 2 or 3 of the fair value hierarchy during the three months ended March 31, 2015.

[2] (2) MSRs with a recorded investment of $21.5 million were reduced by a specific valuation allowance totaling $1.1 million to a reported carrying value of $20.4 million resulting in recognition of $0.2 million in expense included in loan sales and servicing income in the three months ended March 31, 2015.

[3] (3) Collateral dependent impaired loans with a recorded investment of $75.6 million were reduced by specific valuation allowance allocations totaling $11.8 million to a reported net carrying value of $63.8 million.

[4] (4) Amounts do not include assets held at cost at March 31, 2015. During the three months ended March 31, 2015, the re-measurement of foreclosed assets at fair value subsequent to initial recognition resulted in losses of $0.9 million included in noninterest expense.

[5] (5) Amounts do not include assets held at cost at March 31, 2015. During the three months ended March 31, 2015, the re-measurement of covered foreclosed assets at fair value subsequent to initial recognition resulted in losses of $0.1 million included in noninterest expense.

[6] (1) Included in "Other assets" on the Consolidated Balance Sheets(2) Included in "Other liabilities" on the Consolidated Balance Sheets