Fair Value Measurements Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Financial assets
Cash and due from banks	$ 526,951	$ 455,482
Cash and due from banks, Fair Value	526,951	455,482
Interest-bearing deposits in other financial institutions	92,071	126,018
Interest-bearing deposits in other financial institutions, Fair value	92,071	126,018
Federal funds sold and securities purchased under agreements to resell	4,400	20,745
Federal funds sold and securities purchased under agreements to resell, Fair value	4,400	20,745
Investment securities held to maturity, carrying amount	193,759	175,210
Investment securities held to maturity, fair value	193,146	169,889
Investment securities available for sale, fair value	5,277,908	5,250,585
Investment securities available for sale, fair value	5,277,908	5,250,585
Federal Home Loan Bank and Federal Reserve Bank stocks, carrying amount	181,360	181,249
Federal Home Loan Bank and Federal Reserve Bank stocks, Fair value	181,360	181,249
Loans held for sale	46,529	64,738
Loans held for sale, fair value	46,529	64,738
Loans, net	16,173,528	15,627,946
Loans, net Fair value	16,224,051	15,599,094
Bank owned life insurance, carrying amount	568,631	568,413
Bank owned life insurance, Fair value	568,631	568,413
Accrued interest receivable, carrying amount	69,317	66,308
Accrued interest receivable, Fair value	69,317	66,308
Interest rate-related agreements (1), carrying amount	40,078	42,980
Interest rate-related agreements (1), fair value	40,078	42,980
Foreign currency exchange forwards	744	748
Foreign currency exchange forwards, Fair value	744	748
Interest rate lock commitments to originate residential mortgage loans held for sale	791	416
Interest rate lock commitments to originate residential mortgage loans held for sale, fair value	791	416
Forward commitments to sell residential mortgage loans, carrying value	512	1,301
Forward commitments to sell residential mortgage loans, fair value	512	1,301
Purchased options (time deposit), carrying value	7,490	7,328
Purchased options (time deposit), fair value	7,490	7,328
Financial liabilities
Noninterest-bearing demand, savings, interest-bearing demand, and money market deposits	15,885,280	15,581,971
Noninterest-bearing demand, savings, interest-bearing demand, and money market deposits, Fair value	15,885,280	15,581,971
Brokered CDs and other time deposits	1,624,647	1,685,196
Brokered CDs and other time deposits, Fair value	1,626,978	1,687,198
Short-term funding	1,247,906	740,926
Short-term funding, Fair value	1,247,906	740,926
Long-term funding	2,932,040	3,087,267
Long-term funding, fair value	2,924,315	3,085,893
Accrued interest payable	1,520	7,994
Accrued interest payable, Fair value	1,520	7,994
Interest rate-related agreements (1)	42,843	45,815
Interest rate-related agreements (1), Fair value	42,843	45,815
Foreign currency exchange forwards	607	655
Foreign currency exchange forwards, Fair value	607	655
Standby letters of credit (2), carrying amount	3,844	3,754
Standby letters of credit (2), Fair value	3,844	3,754
Forward commitments to sell residential mortgage loans	0	0
Forward commitments to sell residential mortgage loans, fair value	0	0
Written options (time deposit), carrying value	7,490	7,328
Written option (time deposit), fair value	7,490	7,328
Fair Value, Inputs, Level 1 [Member]
Financial assets
Cash and due from banks, Fair Value	526,951	455,482
Interest-bearing deposits in other financial institutions, Fair value	92,071	126,018
Federal funds sold and securities purchased under agreements to resell, Fair value	4,400	20,745
Investment securities held to maturity, fair value	0	0
Investment securities available for sale, fair value	4,249	4,240
Federal Home Loan Bank and Federal Reserve Bank stocks, Fair value	0	0
Loans held for sale, fair value	0	0
Loans, net Fair value	0	0
Bank owned life insurance, Fair value	0	0
Accrued interest receivable, Fair value	69,317	66,308
Interest rate-related agreements (1), fair value	0	0
Foreign currency exchange forwards, Fair value	0	0
Interest rate lock commitments to originate residential mortgage loans held for sale, fair value	0	0
Forward commitments to sell residential mortgage loans, fair value	0	0
Purchased options (time deposit), fair value	0	0
Financial liabilities
Noninterest-bearing demand, savings, interest-bearing demand, and money market deposits, Fair value	0	0
Brokered CDs and other time deposits, Fair value	0	0
Short-term funding, Fair value	0	0
Long-term funding, fair value	0	0
Accrued interest payable, Fair value	1,520	7,994
Interest rate-related agreements (1), Fair value	0	0
Foreign currency exchange forwards, Fair value	0	0
Standby letters of credit (2), Fair value	0	0
Forward commitments to sell residential mortgage loans	0	0
Written option (time deposit), fair value	0	0
Fair Value, Inputs, Level 2 [Member]
Financial assets
Cash and due from banks, Fair Value	0	0
Interest-bearing deposits in other financial institutions, Fair value	0	0
Federal funds sold and securities purchased under agreements to resell, Fair value	0	0
Investment securities held to maturity, fair value	193,146	169,889
Investment securities available for sale, fair value	5,273,432	5,246,046
Federal Home Loan Bank and Federal Reserve Bank stocks, Fair value	181,360	181,249
Loans held for sale, fair value	46,529	64,738
Loans, net Fair value	0	0
Bank owned life insurance, Fair value	568,631	568,413
Accrued interest receivable, Fair value	0	0
Interest rate-related agreements (1), fair value	40,078	42,980
Foreign currency exchange forwards, Fair value	744	748
Interest rate lock commitments to originate residential mortgage loans held for sale, fair value	0	0
Forward commitments to sell residential mortgage loans, fair value	0	0
Purchased options (time deposit), fair value	7,490	7,328
Financial liabilities
Noninterest-bearing demand, savings, interest-bearing demand, and money market deposits, Fair value	0	0
Brokered CDs and other time deposits, Fair value	1,626,978	1,687,198
Short-term funding, Fair value	1,247,906	740,926
Long-term funding, fair value	2,924,315	3,085,893
Accrued interest payable, Fair value	0	0
Interest rate-related agreements (1), Fair value	42,843	45,815
Foreign currency exchange forwards, Fair value	607	655
Standby letters of credit (2), Fair value	3,844	3,754
Forward commitments to sell residential mortgage loans	0	0
Written option (time deposit), fair value	7,490	7,328
Fair Value, Inputs, Level 3 [Member]
Financial assets
Cash and due from banks, Fair Value	0	0
Interest-bearing deposits in other financial institutions, Fair value	0	0
Federal funds sold and securities purchased under agreements to resell, Fair value	0	0
Investment securities held to maturity, fair value	0	0
Investment securities available for sale, fair value	227	299
Federal Home Loan Bank and Federal Reserve Bank stocks, Fair value	0	0
Loans held for sale, fair value	0	0
Loans, net Fair value	16,224,051	15,599,094
Bank owned life insurance, Fair value	0	0
Accrued interest receivable, Fair value	0	0
Interest rate-related agreements (1), fair value	0	0
Foreign currency exchange forwards, Fair value	0	0
Interest rate lock commitments to originate residential mortgage loans held for sale, fair value	791	416
Forward commitments to sell residential mortgage loans, fair value	512	1,301
Purchased options (time deposit), fair value	0	0
Financial liabilities
Noninterest-bearing demand, savings, interest-bearing demand, and money market deposits, Fair value	15,885,280	15,581,971
Brokered CDs and other time deposits, Fair value	0	0
Short-term funding, Fair value	0	0
Long-term funding, fair value	0	0
Accrued interest payable, Fair value	0	0
Interest rate-related agreements (1), Fair value	0	0
Foreign currency exchange forwards, Fair value	0	0
Standby letters of credit (2), Fair value	0	0
Forward commitments to sell residential mortgage loans	0	0
Written option (time deposit), fair value	$ 0	$ 0