Fair Value Measurements Fair Value Measurements (Details 6) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 209,598	$ 164,757
Interest-earning deposits in financial institutions	431,033	148,469
Available-for-sale Securities	1,698,158	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	1,719	3,691
Cost Method Investments, Fair Value Disclosure	2,320	3,691
Equity Method Investments	20,990	21,461
Equity Method Investments, Fair Value Disclosure	21,250	21,700
Loans and leases, net	11,934,814	11,797,977
Loans Receivable, Fair Value Disclosure	12,008,957	11,757,951
Derivative Asset	8,810	5,234
Derivative Asset, Fair Value, Gross Asset	8,810
Deposits, Savings Deposits	7,236,531	6,256,190
Time Deposits	5,345,285	5,498,938
Deposits, Fair Value Disclosure	5,351,765	5,502,479
Borrowed Funds	2,751	383,402
Long-term Debt, Fair Value	3,099	383,539
Subordinated debentures	433,944	433,583
Subordinated Debt Obligations, Fair Value Disclosure	417,706	417,657
Derivative Liability	725	118
Derivative Liability, Fair Value, Gross Liability	725
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	209,598	164,757
Interest-earning deposits in financial institutions	431,033	148,469
Available-for-sale Securities	518	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	0
Loans Receivable, Fair Value Disclosure		0
Derivative Asset, Fair Value, Gross Asset	0
Deposits, Savings Deposits	0	0
Deposits, Fair Value Disclosure	0	0
Long-term Debt, Fair Value	0	380,000
Subordinated Debt Obligations, Fair Value Disclosure	0	0
Derivative Liability, Fair Value, Gross Liability	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	1,665,317	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	0
Loans Receivable, Fair Value Disclosure		2,366
Derivative Asset, Fair Value, Gross Asset	8,810
Deposits, Savings Deposits	7,236,531	6,256,190
Deposits, Fair Value Disclosure	5,351,765	5,502,479
Long-term Debt, Fair Value	3,099	3,539
Subordinated Debt Obligations, Fair Value Disclosure	417,706	417,657
Derivative Liability, Fair Value, Gross Liability	725
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	32,323	33,947
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	0	0
Cost Method Investments, Fair Value Disclosure	2,320	3,691
Equity Method Investments, Fair Value Disclosure	21,250	21,700
Loans Receivable, Fair Value Disclosure	12,008,405	11,755,585
Derivative Asset, Fair Value, Gross Asset	0
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
Derivative Liability, Fair Value, Gross Liability	$ 0