Fair Value Measurements (Details 8) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 235,061	$ 233,215
Interest-earning deposits in financial institutions	312,735	165,222
Securities available-for-sale, Carrying Amount		3,774,431
Securities available-for-sale, at fair value	3,801,986	3,774,431
Investment in FHLB stock, Carrying Amount	17,250	20,790
Investment in FHLB stock, Fair Value	17,250	20,790
Trade and Loans Receivables Held-for-sale, Net, Not Part of Disposal Group	0	481,100
Loans Held-for-sale, Fair Value Disclosure		483,563
Loans and leases, net	16,321,010	16,833,287
Loans and leases held for investment, net	16,247,325
Warrants and Rights Outstanding		5,161
Equity warrants		5,161
Other derivative assets, Carrying Amount	3,327	1,873
Fair Value, Estimate Not Practicable, Equity Method Investments	5,028
Demand, interest checking, money market, and savings deposits	15,661,529	15,937,012
Interest-bearing Domestic Deposit, Brokered	585,399	863,202
Time deposits	1,831,860	2,065,322
Time deposits	1,820,330	2,055,104
Borrowings	575,284	467,342
Borrowings	575,285	467,342
Subordinated debentures	452,223	462,437
Subordinated debentures	435,985	444,383
Derivative Liability	642	1,379
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	235,061	233,215
Interest-earning deposits in financial institutions	312,735	165,222
Securities available-for-sale, at fair value		5,922
Investment in FHLB stock, Fair Value	0	0
Demand, interest checking, money market, and savings deposits	0	0
Interest-bearing Domestic Deposit, Brokered	0	0
Time deposits	0	0
Borrowings	575,000	467,000
Subordinated debentures	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
Securities available-for-sale, at fair value		3,703,526
Investment in FHLB stock, Fair Value	17,250	20,790
Demand, interest checking, money market, and savings deposits	15,661,529	15,937,012
Interest-bearing Domestic Deposit, Brokered	585,399	863,202
Time deposits	1,820,330	2,055,104
Borrowings	285	342
Subordinated debentures	435,985	444,383
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
Securities available-for-sale, at fair value		64,983
Investment in FHLB stock, Fair Value	0	0
Loans and leases held for investment, net	16,246,197
Demand, interest checking, money market, and savings deposits	0	0
Interest-bearing Domestic Deposit, Brokered	0	0
Time deposits	0	0
Borrowings	0	0
Subordinated debentures	0	0
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	3,801,986	3,774,431
Equity warrants	5,284	5,161
Other derivative assets, Fair Value	3,327	1,873
Derivative liabilities	642	1,379
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	148,582	5,922
Equity warrants	0	0
Other derivative assets, Fair Value	0	0
Fair Value, Estimate Not Practicable, Equity Method Investments	5,028
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	3,594,905	3,703,526
Equity warrants	0	0
Other derivative assets, Fair Value	3,327	1,873
Fair Value, Estimate Not Practicable, Equity Method Investments	0
Derivative liabilities	642	1,379
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	58,499	64,983
Equity warrants	5,284	5,161
Other derivative assets, Fair Value	0	0
Fair Value, Estimate Not Practicable, Equity Method Investments	0
Derivative liabilities	0	0
Non Purchased Credit Impaired Loans and Leases | Fair Value, Measurements, Nonrecurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Held-for-sale, Fair Value Disclosure		0
Non Purchased Credit Impaired Loans and Leases | Fair Value, Measurements, Nonrecurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Held-for-sale, Fair Value Disclosure		483,563
Non Purchased Credit Impaired Loans and Leases | Fair Value, Measurements, Nonrecurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Held-for-sale, Fair Value Disclosure		0
NonPCI and PCI Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases, net		16,833,287
Loans and leases held for investment, net		17,023,098
NonPCI and PCI Loans | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment, net	0	0
NonPCI and PCI Loans | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment, net	$ 1,128	5,143
NonPCI and PCI Loans | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment, net		$ 17,017,955