Fair Value Measurements (Details 8) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 147,579	$ 337,965
Interest-earning deposits in financial institutions	122,439	81,705
Securities available-for-sale, Carrying Amount		3,223,830
Securities available-for-sale, at fair value	3,532,230	3,223,830
Investment in FHLB stock, Carrying Amount	17,250	21,870
Investment in FHLB stock, Fair Value	17,250	21,870
Investments carried at cost, Carrying Amount	1,006	1,416
Investments carried at cost, Fair Value	10,702	3,843
Loans and leases, net	15,530,911	15,298,716
Loans and leases held for investment, net	15,700,815
Warrants and Rights Outstanding		5,497
Equity warrants		5,497
Other derivative assets, Carrying Amount	1,221	694
Demand, interest checking, money market, and savings deposits	13,531,300	12,523,834
Interest-bearing Domestic Deposit, Brokered	1,118,694	1,174,487
Time deposits	2,123,251	2,172,290
Time deposits	2,114,655	2,166,187
Borrowings	250,399	905,812
Borrowings	250,399	905,838
Subordinated debentures	448,126	440,744
Subordinated debentures	431,173	424,507
Derivative Liability	564	3,285
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	147,579	337,965
Interest-earning deposits in financial institutions	122,439	81,705
Securities available-for-sale, at fair value		2,080
Investment in FHLB stock, Fair Value	0	0
Investments carried at cost, 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	250,000	591,000
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		3,156,475
Investment in FHLB stock, Fair Value	17,250	21,870
Investments carried at cost, Fair Value	0	0
Demand, interest checking, money market, and savings deposits	13,531,300	12,523,834
Interest-bearing Domestic Deposit, Brokered	1,118,694	1,174,487
Time deposits	2,114,655	2,166,187
Borrowings	399	314,838
Subordinated debentures	431,173	424,507
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		65,275
Investment in FHLB stock, Fair Value	0	0
Investments carried at cost, Fair Value	10,702	3,843
Loans and leases held for investment, net	15,694,036
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	3,532,230	3,223,830
Equity warrants	5,158	5,497
Other derivative assets, Fair Value	1,221	694
Derivative liabilities	564	3,285
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	4,808	2,080
Equity warrants	0	0
Other derivative assets, Fair Value	0	0
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	3,447,101	3,156,475
Equity warrants	0	0
Other derivative assets, Fair Value	1,221	694
Derivative liabilities	564	3,285
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	80,321	65,275
Equity warrants	5,158	5,497
Other derivative assets, Fair Value	0	0
Derivative liabilities	0	0
NonPCI and PCI Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases, net		15,298,716
Loans and leases held for investment, net		15,494,808
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	$ 6,779	1,661
NonPCI and PCI Loans | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment, net		$ 15,493,147