Loans and Leases (Details 3) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017		Mar. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		$ 16,455,285	$ 16,972,743
Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		208,042
Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		415,116
Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		15,832,127
Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment			16,914,707	[1],[2],[3]	$ 15,460,354
Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		278,405
Non Purchased Credit Impaired Loans and Leases | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		302,168
Non Purchased Credit Impaired Loans and Leases | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		16,334,134
Real Estate Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		7,554,243
Real Estate Mortgage | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		57,071
Real Estate Mortgage | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		160,168
Real Estate Mortgage | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		7,337,004
Real Estate Mortgage | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment			7,798,991	[1],[2]	5,886,969
Real Estate Mortgage | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		102,220
Real Estate Mortgage | Non Purchased Credit Impaired Loans and Leases | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		127,070
Real Estate Mortgage | Non Purchased Credit Impaired Loans and Leases | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		7,569,701
Real Estate Mortgage | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		5,033,006
Real Estate Mortgage | Commercial real estate | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		44,635
Real Estate Mortgage | Commercial real estate | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		158,496
Real Estate Mortgage | Commercial real estate | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		4,829,875
Real Estate Mortgage | Commercial real estate | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1],[2]		5,361,487
Real Estate Mortgage | Commercial real estate | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		93,795
Real Estate Mortgage | Commercial real estate | Non Purchased Credit Impaired Loans and Leases | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		122,488
Real Estate Mortgage | Commercial real estate | Non Purchased Credit Impaired Loans and Leases | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		5,145,204
Real Estate Mortgage | Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		2,521,237
Real Estate Mortgage | Residential Real Estate | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		12,436
Real Estate Mortgage | Residential Real Estate | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,672
Real Estate Mortgage | Residential Real Estate | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		2,507,129
Real Estate Mortgage | Residential Real Estate | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1],[2]		2,437,504
Real Estate Mortgage | Residential Real Estate | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		8,425
Real Estate Mortgage | Residential Real Estate | Non Purchased Credit Impaired Loans and Leases | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		4,582
Real Estate Mortgage | Residential Real Estate | Non Purchased Credit Impaired Loans and Leases | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		2,424,497
Real Estate Construction and Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,677,002
Real Estate Construction and Land | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		453
Real Estate Construction and Land | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		30,626
Real Estate Construction and Land | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,645,923
Real Estate Construction and Land | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment			1,591,229	[1],[2]	1,108,236
Real Estate Construction and Land | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		0
Real Estate Construction and Land | Non Purchased Credit Impaired Loans and Leases | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		619
Real Estate Construction and Land | Non Purchased Credit Impaired Loans and Leases | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		1,590,610
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		789,892
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		453
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		0
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		789,439
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1],[2]		769,075
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		0
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Non Purchased Credit Impaired Loans and Leases | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		0
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Non Purchased Credit Impaired Loans and Leases | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		769,075
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		887,110
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		0
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		30,626
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		856,484
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1],[2]		822,154
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		0
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Non Purchased Credit Impaired Loans and Leases | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		619
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Non Purchased Credit Impaired Loans and Leases | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		821,535
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		6,826,123
Commercial | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		150,090
Commercial | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		222,866
Commercial | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		6,453,167
Commercial | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment			7,114,920	[1],[2]	8,082,678
Commercial | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		175,922
Commercial | Non Purchased Credit Impaired Loans and Leases | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		173,349
Commercial | Non Purchased Credit Impaired Loans and Leases | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		6,765,649
Commercial | Asset Based
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		2,957,890
Commercial | Asset Based | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		49,913
Commercial | Asset Based | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		54,882
Commercial | Asset Based | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		2,853,095
Commercial | Asset Based | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1],[2]		2,924,871
Commercial | Asset Based | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		51,000
Commercial | Asset Based | Non Purchased Credit Impaired Loans and Leases | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		37,256
Commercial | Asset Based | Non Purchased Credit Impaired Loans and Leases | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		2,836,615
Commercial | Venture Capital Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,920,643
Commercial | Venture Capital Loans | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		31,364
Commercial | Venture Capital Loans | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		124,303
Commercial | Venture Capital Loans | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,764,976
Commercial | Venture Capital Loans | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1],[2]		2,122,711
Commercial | Venture Capital Loans | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		49,671
Commercial | Venture Capital Loans | Non Purchased Credit Impaired Loans and Leases | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		114,210
Commercial | Venture Capital Loans | Non Purchased Credit Impaired Loans and Leases | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		1,958,830
Commercial | Other Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,947,590
Commercial | Other Commercial | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		68,813
Commercial | Other Commercial | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		43,681
Commercial | Other Commercial | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,835,096
Commercial | Other Commercial | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1],[2]		2,067,338
Commercial | Other Commercial | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		75,251
Commercial | Other Commercial | Non Purchased Credit Impaired Loans and Leases | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		21,883
Commercial | Other Commercial | Non Purchased Credit Impaired Loans and Leases | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		1,970,204
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		397,917
Consumer | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		428
Consumer | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,456
Consumer | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		$ 396,033
Consumer | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment			409,567	[1],[2]	$ 382,471
Consumer | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		263
Consumer | Non Purchased Credit Impaired Loans and Leases | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		1,130
Consumer | Non Purchased Credit Impaired Loans and Leases | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[1]		$ 408,174

[1] Excludes loans held for sale carried at lower of cost or fair value and PCI loans.

[2] Excludes loans held for sale carried at lower of cost or fair value and PCI loans.

[3] Excludes loans held for sale carried at lower of cost or fair value and PCI loans.