Fair Value Measurements Fair Value Measurements (Details 7) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 164,757	$ 96,424
Interest-earning deposits in financial institutions	148,469	50,998
Available-for-sale Securities	1,567,177	1,494,745
Federal Home Loan Bank stock, at cost	40,609	27,939
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	40,609	27,939
Cost Method Investments	3,691
Cost Method Investments, Fair Value Disclosure	3,691
Equity Method Investments	21,461
Equity Method Investments, Fair Value Disclosure	21,700
Loans and leases, net	11,797,977	4,230,318
Loans Receivable, Fair Value Disclosure	11,757,951	4,231,078
Derivative Asset	5,234
Derivative Asset, Fair Value of Collateral	5,234
Deposits, Savings Deposits	6,256,190	4,616,616
Time Deposits	5,498,938	664,371
Deposits, Fair Value Disclosure	5,202,464	665,148
Borrowed Funds	383,402	113,726
Long-term Debt, Fair Value	383,539	113,726
Subordinated debentures	433,583	132,645
Subordinated Debt Obligations, Fair Value Disclosure	417,657	132,498
Derivative Liability	118
Derivative Liability, Fair Value of Collateral	118
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	164,757	96,424
Interest-earning deposits in financial institutions	148,469	50,998
Available-for-sale Securities		507
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	0	0
Cost Method Investments, Fair Value Disclosure	0
Equity Method Investments, Fair Value Disclosure	0
Loans Receivable, Fair Value Disclosure		0
Derivative Asset, Fair Value of Collateral	0
Deposits, Savings Deposits	0	0
Deposits, Fair Value Disclosure	0	0
Long-term Debt, Fair Value	380,000	106,600
Subordinated Debt Obligations, Fair Value Disclosure	0	0
Derivative Liability, Fair Value of Collateral	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		1,456,334
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	40,609	27,939
Cost Method Investments, Fair Value Disclosure	0
Equity Method Investments, Fair Value Disclosure	0
Loans Receivable, Fair Value Disclosure		2,051
Derivative Asset, Fair Value of Collateral	5,234
Deposits, Savings Deposits	6,256,190	4,616,616
Deposits, Fair Value Disclosure	5,202,464	665,148
Long-term Debt, Fair Value	3,539	7,126
Subordinated Debt Obligations, Fair Value Disclosure	417,657	132,498
Derivative Liability, Fair Value of Collateral	118
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		37,904
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	0	0
Cost Method Investments, Fair Value Disclosure	3,691
Equity Method Investments, Fair Value Disclosure	21,700
Loans Receivable, Fair Value Disclosure	11,755,585	4,229,027
Derivative Asset, Fair Value of Collateral	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 of Collateral	$ 0