Fair Value Measurements (Details 6) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 154,652	$ 164,757
Interest-earning deposits in financial institutions	81,642	148,469
Available-for-sale Securities	1,809,364	1,567,177
Federal Home Loan Bank stock, at cost	17,250	40,609
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	17,250	40,609
Cost Method Investments	1,420	3,691
Cost Method Investments, Fair Value Disclosure	9,300	3,691
Equity Method Investments		21,461
Equity Method Investments, Fair Value Disclosure		21,700
Loans and leases, net	12,348,934	11,797,977
Loans Receivable, Fair Value Disclosure	12,254,393	11,757,951
Derivative Asset	10,576	5,234
Deposits, Savings Deposits	7,528,467	6,256,190
Time Deposits	4,587,296	5,498,938
Deposits, Fair Value Disclosure	4,588,540	5,502,479
Borrowed Funds	552,497	383,402
Long-term Debt, Fair Value	552,570	383,539
Subordinated debentures	435,417	433,583
Subordinated Debt Obligations, Fair Value Disclosure	419,180	417,657
Derivative Liability	526	118
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	154,652	164,757
Interest-earning deposits in financial institutions	81,642	148,469
Available-for-sale Securities	522	519
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	0	0
Cost Method Investments, Fair Value Disclosure	0	0
Equity Method Investments, Fair Value Disclosure		0
Loans Receivable, Fair Value Disclosure		0
Deposits, Savings Deposits	0	0
Deposits, Fair Value Disclosure	0	0
Long-term Debt, Fair Value	550,000	380,000
Subordinated Debt Obligations, Fair Value Disclosure	0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	0	0
Interest-earning deposits in financial institutions	0	0
Available-for-sale Securities	1,777,816	1,532,711
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	17,250	40,609
Cost Method Investments, Fair Value Disclosure	0	0
Equity Method Investments, Fair Value Disclosure		0
Loans Receivable, Fair Value Disclosure		2,366
Deposits, Savings Deposits	7,528,467	6,256,190
Deposits, Fair Value Disclosure	4,588,540	5,502,479
Long-term Debt, Fair Value	2,570	3,539
Subordinated Debt Obligations, Fair Value Disclosure	419,180	417,657
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	0	0
Interest-earning deposits in financial institutions	0	0
Available-for-sale Securities	31,026	33,947
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	0	0
Cost Method Investments, Fair Value Disclosure	9,300	3,691
Equity Method Investments, Fair Value Disclosure		21,700
Loans Receivable, Fair Value Disclosure	12,251,837	11,755,585
Deposits, Savings Deposits	0	0
Deposits, Fair Value Disclosure	0	0
Long-term Debt, Fair Value	0	0
Subordinated Debt Obligations, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities	1,809,364	1,567,177
Derivative Asset, Fair Value of Collateral	10,576	5,234
Derivative Liability, Fair Value of Collateral	526	118
Fair Value, Measurements, Recurring [Member] | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities		519
Derivative Asset, Fair Value of Collateral	0	0
Derivative Liability, Fair Value of Collateral	0	0
Fair Value, Measurements, Recurring [Member] | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities		1,532,711
Derivative Asset, Fair Value of Collateral	10,576	5,234
Derivative Liability, Fair Value of Collateral	526	118
Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities		33,947
Derivative Asset, Fair Value of Collateral	0	0
Derivative Liability, Fair Value of Collateral	$ 0	$ 0