Loans and Leases (Details 3) - USD ($) $ in Thousands		Jun. 30, 2018	Dec. 31, 2017		Jun. 30, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		$ 16,885,192	$ 16,972,743
Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		236,292
Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		506,848
Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		16,142,052
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]	$ 15,471,031
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		7,566,374
Real Estate Mortgage | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		82,483
Real Estate Mortgage | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		245,212
Real Estate Mortgage | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		7,238,679
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]	6,071,798
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		5,010,680
Real Estate Mortgage | Commercial real estate | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		71,030
Real Estate Mortgage | Commercial real estate | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		243,045
Real Estate Mortgage | Commercial real estate | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		4,696,605
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		2,555,694
Real Estate Mortgage | Residential Real Estate | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		11,453
Real Estate Mortgage | Residential Real Estate | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		2,167
Real Estate Mortgage | Residential Real Estate | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		2,542,074
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		1,874,026
Real Estate Construction and Land | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		10,898
Real Estate Construction and Land | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		26,839
Real Estate Construction and Land | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,836,289
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]	1,163,340
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		831,462
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		448
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		3,807
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		827,207
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		1,042,564
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		10,450
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		23,032
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		1,009,082
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		7,066,112
Commercial | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		142,477
Commercial | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		233,728
Commercial | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		6,689,907
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]	7,837,667
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		3,184,300
Commercial | Asset Based | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		35,429
Commercial | Asset Based | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		67,628
Commercial | Asset Based | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		3,081,243
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		2,008,205
Commercial | Venture Capital Loans | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		54,219
Commercial | Venture Capital Loans | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		99,485
Commercial | Venture Capital Loans | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,854,501
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		1,873,607
Commercial | Other Commercial | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		52,829
Commercial | Other Commercial | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		66,615
Commercial | Other Commercial | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,754,163
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		378,680
Consumer | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		434
Consumer | Nonclassified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,069
Consumer | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		$ 377,177
Consumer | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment			409,567	[1],[2]	$ 398,226
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.