Loans and Leases (Details 3) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017		Sep. 30, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		$ 17,230,146	$ 16,972,743
Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		260,459
Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		360,058
Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		16,609,629
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]	$ 15,628,023
Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		278,405
Non Purchased Credit Impaired Loans and Leases | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		302,168
Non Purchased Credit Impaired Loans and Leases | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		16,334,134
Real Estate Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		7,678,660
Real Estate Mortgage | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		75,828
Real Estate Mortgage | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		152,647
Real Estate Mortgage | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		7,450,185
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	[2],[3]	6,131,196
Real Estate Mortgage | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		102,220
Real Estate Mortgage | Non Purchased Credit Impaired Loans and Leases | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		127,070
Real Estate Mortgage | Non Purchased Credit Impaired Loans and Leases | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		7,569,701
Real Estate Mortgage | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		4,932,823
Real Estate Mortgage | Commercial | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		64,574
Real Estate Mortgage | Commercial | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		140,611
Real Estate Mortgage | Commercial | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		4,727,638
Real Estate Mortgage | Commercial | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2],[3]		5,361,487
Real Estate Mortgage | Commercial | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		93,795
Real Estate Mortgage | Commercial | Non Purchased Credit Impaired Loans and Leases | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		122,488
Real Estate Mortgage | Commercial | Non Purchased Credit Impaired Loans and Leases | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		5,145,204
Real Estate Mortgage | Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		2,745,837
Real Estate Mortgage | Residential Real Estate | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		11,254
Real Estate Mortgage | Residential Real Estate | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		12,036
Real Estate Mortgage | Residential Real Estate | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		2,722,547
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	[2],[3]		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	[2]		8,425
Real Estate Mortgage | Residential Real Estate | Non Purchased Credit Impaired Loans and Leases | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		4,582
Real Estate Mortgage | Residential Real Estate | Non Purchased Credit Impaired Loans and Leases | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		2,424,497
Real Estate Construction and Land
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		2,000,957
Real Estate Construction and Land | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		442
Real Estate Construction and Land | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		28,478
Real Estate Construction and Land | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,972,037
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	[2],[3]	1,249,222
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	[2]		0
Real Estate Construction and Land | Non Purchased Credit Impaired Loans and Leases | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		619
Real Estate Construction and Land | Non Purchased Credit Impaired Loans and Leases | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		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		854,346
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		442
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		3,833
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		850,071
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	[2],[3]		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	[2]		0
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Non Purchased Credit Impaired Loans and Leases | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		0
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Non Purchased Credit Impaired Loans and Leases | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		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		1,146,611
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 | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		24,645
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,121,966
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	[2],[3]		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	[2]		0
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Non Purchased Credit Impaired Loans and Leases | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		619
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Non Purchased Credit Impaired Loans and Leases | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		821,535
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		7,152,058
Commercial | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		183,754
Commercial | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		177,237
Commercial | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		6,791,067
Commercial | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment			7,114,920	[2],[3]	7,861,692
Commercial | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		175,922
Commercial | Non Purchased Credit Impaired Loans and Leases | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		173,349
Commercial | Non Purchased Credit Impaired Loans and Leases | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		6,765,649
Commercial | Asset Based
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		3,222,311
Commercial | Asset Based | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		42,960
Commercial | Asset Based | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		64,778
Commercial | Asset Based | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		3,114,573
Commercial | Asset Based | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2],[3]		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	[2]		51,000
Commercial | Asset Based | Non Purchased Credit Impaired Loans and Leases | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		37,256
Commercial | Asset Based | Non Purchased Credit Impaired Loans and Leases | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		2,836,615
Commercial | Venture Capital Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		2,031,895
Commercial | Venture Capital Loans | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		47,230
Commercial | Venture Capital Loans | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		65,295
Commercial | Venture Capital Loans | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,919,370
Commercial | Venture Capital Loans | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2],[3]		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	[2]		49,671
Commercial | Venture Capital Loans | Non Purchased Credit Impaired Loans and Leases | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		114,210
Commercial | Venture Capital Loans | Non Purchased Credit Impaired Loans and Leases | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		1,958,830
Commercial | Other Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,897,852
Commercial | Other Commercial | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		93,564
Commercial | Other Commercial | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		47,164
Commercial | Other Commercial | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,757,124
Commercial | Other Commercial | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2],[3]		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	[2]		75,251
Commercial | Other Commercial | Non Purchased Credit Impaired Loans and Leases | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		21,883
Commercial | Other Commercial | Non Purchased Credit Impaired Loans and Leases | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		1,970,204
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		398,471
Consumer | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		435
Consumer | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		1,696
Consumer | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment		$ 396,340
Consumer | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment			409,567	[2],[3]	$ 385,913
Consumer | Non Purchased Credit Impaired Loans and Leases | Classified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		263
Consumer | Non Purchased Credit Impaired Loans and Leases | Special Mention
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		1,130
Consumer | Non Purchased Credit Impaired Loans and Leases | Pass
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment	[2]		$ 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.