Fair Value Measurement (Recurring and Nonrecurring Table) (Details) (USD $)	3 Months Ended				12 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral Dependant Impaired and Non Accrual Loans Carrying Amount	$ 55,400,000		$ 48,100,000		$ 47,900,000
Recurring Fair Value Measurements
Available-for-sale	3,462,990,000		3,256,259,000		3,273,174,000
Residential loans held for sale	19,512,000		17,813,000		11,622,000
Derivative Asset, Fair Value, Gross Asset	43,097,000		53,839,000		47,902,000
Total Assets, Fair Value Disclosure, Recurring	3,525,599,000		3,327,911,000		3,332,698,000
Derivative Liability, Fair Value, Gross Liability	49,280,000		65,506,000		58,201,000
True Up Liability	12,804,000		11,457,000		11,463,000
Total liabilities at fair value on a recurring basis	62,084,000	[1]	76,963,000		69,664,000	[1]
Nonrecurring Fair Value Measurements [Abstract]
Fair Value of Mortgage Servicing Rights	22,229,000	[2]	22,616,000		23,041,000	[2]
Impaired and Non Accrual Loans Fair Value Disclosure	55,406,000	[3]	48,129,000		47,870,000	[3]
Other Real Estate, Non Covered	14,896,000	[4]	13,413,000		10,018,000	[4]
Other Real Estate Covered by Loss Share	5,798,000	[5]	8,475,000		8,754,000	[5]
Nonrecurring Fair Value	98,329,000		92,633,000		89,683,000
Impairment of Noncovered Other Real Estate Owned	700,000		300,000		1,400,000
Impairment of Covered Other Real Esate Owned	100,000		200,000		1,000,000
Level 1
Recurring Fair Value Measurements
Available-for-sale	2,916,000		3,096,000		3,036,000
Residential loans held for sale	0		0		0
Derivative Asset, Fair Value, Gross Asset	0		0		0
Total Assets, Fair Value Disclosure, Recurring	2,916,000		3,096,000		3,036,000
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	3,112,553,000		2,930,401,000		2,922,527,000
Residential loans held for sale	19,512,000		17,813,000		11,622,000
Derivative Asset, Fair Value, Gross Asset	43,097,000		53,839,000		47,902,000
Total Assets, Fair Value Disclosure, Recurring	3,175,162,000		3,002,053,000		2,982,051,000
Derivative Liability, Fair Value, Gross Liability	48,765,000		65,506,000		58,201,000
True Up Liability	0		0		0
Total liabilities at fair value on a recurring basis	48,765,000	[1]	65,506,000		58,201,000	[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	347,521,000		322,762,000		347,611,000
Residential loans held for sale	0		0		0
Derivative Asset, Fair Value, Gross Asset	0		0		0
Total Assets, Fair Value Disclosure, Recurring	347,521,000		322,762,000		347,611,000
Derivative Liability, Fair Value, Gross Liability	515,000		0		0
True Up Liability	12,804,000		11,457,000		11,463,000
Total liabilities at fair value on a recurring basis	13,319,000	[1]	11,457,000		11,463,000	[1]
Nonrecurring Fair Value Measurements [Abstract]
Fair Value of Mortgage Servicing Rights	22,229,000		22,616,000		23,041,000
Impaired and Non Accrual Loans Fair Value Disclosure	55,406,000		48,129,000		47,870,000
Other Real Estate, Non Covered	14,896,000		13,413,000		10,018,000	[4]
Other Real Estate Covered by Loss Share	5,798,000		8,475,000		8,754,000	[5]
Nonrecurring Fair Value	98,329,000		92,633,000		89,683,000
Equity Securities
Recurring Fair Value Measurements
Available-for-sale	2,916,000		3,096,000		3,036,000
Equity Securities | Level 1
Recurring Fair Value Measurements
Available-for-sale			3,096,000		3,036,000
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 [Member]
Recurring Fair Value Measurements
Available-for-sale	2,500,000		3,281,000		3,281,000
Non-marketable Equity Securities [Member] | Level 1
Recurring Fair Value Measurements
Available-for-sale	0				0
Non-marketable Equity Securities [Member] | Level 2
Recurring Fair Value Measurements
Available-for-sale	0		10,000		10,000
Non-marketable Equity Securities [Member] | Level 3
Recurring Fair Value Measurements
Available-for-sale			3,271,000		3,271,000
U.S. States and political subdivisions debt securities
Recurring Fair Value Measurements
Available-for-sale	237,067,000		272,224,000		262,367,000
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			272,224,000		262,367,000
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	996,387,000		999,375,000		969,922,000
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			999,375,000		969,922,000
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	84,764,000		55,932,000		69,567,000
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			55,932,000		69,567,000
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	1,600,317,000		1,505,706,000		1,518,393,000
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			1,505,706,000		1,518,393,000
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	7,000		9,000		9,000
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		0		0
Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency | Level 3
Recurring Fair Value Measurements
Available-for-sale	6,000		9,000		9,000
Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Recurring Fair Value Measurements
Available-for-sale	194,017,000		97,154,000		102,268,000
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			97,154,000		102,268,000
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	54,594,000		50,850,000		50,644,000
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			50,850,000		50,644,000
Collateralized Loan Obligations
Recurring Fair Value Measurements
Available-for-sale	290,421,000		268,632,000		293,687,000
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			268,632,000		293,687,000
Not Designated as Hedging Instrument
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset	43,097,000	[6]	53,839,000	[6]	47,902,000	[6]
Derivative Liability, Fair Value, Gross Liability	41,696,000		52,217,000		46,627,000
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	0		0	[6]	0	[6]
Derivative Liability, Fair Value, Gross Liability	7,584,000		13,289,000		11,574,000
Interest Rate Swap | Designated as Hedging Instrument | Level 1
Recurring Fair Value Measurements
Derivative Liability, Fair Value, Gross Liability	0		0		0
Interest Rate Swap | Designated as Hedging Instrument | Level 2
Recurring Fair Value Measurements
Derivative Liability, Fair Value, Gross Liability			13,289,000		11,574,000
Interest Rate Swap | Designated as Hedging Instrument | Level 3
Recurring Fair Value Measurements
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	40,937,000		51,044,000	[6]	46,577,000	[6]
Derivative Liability, Fair Value, Gross Liability	40,937,000		51,044,000		46,577,000
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			51,044,000		46,577,000
Derivative Liability, Fair Value, Gross Liability			51,044,000		46,577,000
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	1,975,000		2,729,000	[6]	891,000	[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			2,729,000		891,000
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	0		0	[6]	384,000	[6]
Derivative Liability, Fair Value, Gross Liability	91,000		1,081,000		0
Forward sales contracts | Not Designated as Hedging Instrument | Level 1
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset					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					384,000
Derivative Liability, Fair Value, Gross Liability			1,081,000
Forward sales contracts | Not Designated as Hedging Instrument | Level 3
Recurring Fair Value Measurements
Derivative Asset, Fair Value, Gross Asset					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	185,000		66,000	[6]	50,000	[6]
Derivative Liability, Fair Value, Gross Liability	153,000		92,000		50,000
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			66,000		50,000
Derivative Liability, Fair Value, Gross Liability			92,000		50,000
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	515,000		0		0
Other Contract | Not Designated as Hedging Instrument | Level 1
Recurring Fair Value Measurements
Derivative Liability, Fair Value, Gross Liability	$ 0

[1] (a) - There were no transfers between levels 1, 2 or 3 of the fair value hierarchy during the three months ended September 30, 2014.

[2] (b) - MSRs with a recorded investment of $22.2 million were reduced by a specific valuation allowance totaling $0.5 million to a reported carrying value of $21.7 million resulting in recognition of $0.1 million in recoveries included in loans sales and servicing income in the three months ended September 30, 2014.

[3] (c) - Collateral dependent impaired loans with a recorded investment of $59.9 million were reduced by specific valuation allowance allocations totaling $4.5 million to a reported net carrying value of $55.4 million.

[4] (d) - Amounts do not include assets held at cost at September 30, 2014. During the three months ended September 30, 2014, the re-measurement of foreclosed assets at fair value subsequent to initial recognition resulted in losses of $0.7 million included in noninterest expense.

[5] (e) - Amounts do not include assets held at cost at September 30, 2014. During the three months ended September 30, 2014, the re-measurement of covered foreclosed assets at fair value subsequent to initial recognition resulted in losses $0.1 million included in noninterest expense.

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