Loans and Leases (Details 2) - USD ($) $ in Thousands		Jun. 30, 2018	Dec. 31, 2017		Jun. 30, 2017
Financing Receivable, Impaired [Line Items]
Nonaccrual		$ 113,745	$ 155,784	[1]
Loans held for investment		16,885,192	16,972,743
Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	[2]		155,784
Loans held for investment			16,914,707	[2],[3],[4]	$ 15,471,031
Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		16,771,447
Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	[2]		16,758,923
Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Nonaccrual		36,632
Loans held for investment		7,566,374
Real Estate Mortgage | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	[1],[2]		68,913
Loans held for investment			7,798,991	[2],[3]	6,071,798
Real Estate Mortgage | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		7,529,742
Real Estate Mortgage | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	[2]		7,730,078
Real Estate Mortgage | Commercial real estate
Financing Receivable, Impaired [Line Items]
Nonaccrual		33,105
Loans held for investment		5,010,680
Real Estate Mortgage | Commercial real estate | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	[2]		65,563
Loans held for investment	[2],[3]		5,361,487
Real Estate Mortgage | Commercial real estate | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		4,977,575
Real Estate Mortgage | Commercial real estate | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	[2]		5,295,924
Real Estate Mortgage | Residential Real Estate
Financing Receivable, Impaired [Line Items]
Nonaccrual		3,527
Loans held for investment		2,555,694
Real Estate Mortgage | Residential Real Estate | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	[2]		3,350
Loans held for investment	[2],[3]		2,437,504
Real Estate Mortgage | Residential Real Estate | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		2,552,167
Real Estate Mortgage | Residential Real Estate | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	[2]		2,434,154
Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Nonaccrual		10,450
Loans held for investment		1,874,026
Real Estate Construction and Land | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	[1],[2]		0
Loans held for investment			1,591,229	[2],[3]	1,163,340
Real Estate Construction and Land | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		1,863,576
Real Estate Construction and Land | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	[2]		1,591,229
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable
Financing Receivable, Impaired [Line Items]
Nonaccrual		0
Loans held for investment		831,462
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	[2]		0
Loans held for investment	[2],[3]		769,075
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		831,462
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	[2]		769,075
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable
Financing Receivable, Impaired [Line Items]
Nonaccrual		10,450
Loans held for investment		1,042,564
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	[2]		0
Loans held for investment	[2],[3]		822,154
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		1,032,114
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	[2]		822,154
Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual		66,399
Loans held for investment		7,066,112
Commercial | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	[1],[2]		86,851
Loans held for investment			7,114,920	[2],[3]	7,837,667
Commercial | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		6,999,713
Commercial | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	[2]		7,028,069
Commercial | Asset Based
Financing Receivable, Impaired [Line Items]
Nonaccrual		29,677
Loans held for investment		3,184,300
Commercial | Asset Based | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	[2]		33,553
Loans held for investment	[2],[3]		2,924,871
Commercial | Asset Based | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		3,154,623
Commercial | Asset Based | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	[2]		2,891,318
Commercial | Venture Capital Loans
Financing Receivable, Impaired [Line Items]
Nonaccrual		27,940
Loans held for investment		2,008,205
Commercial | Venture Capital Loans | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	[2]		29,424
Loans held for investment	[2],[3]		2,122,711
Commercial | Venture Capital Loans | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		1,980,265
Commercial | Venture Capital Loans | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	[2]		2,093,287
Commercial | Other Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual		8,782
Loans held for investment		1,873,607
Commercial | Other Commercial | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	[2]		23,874
Loans held for investment	[2],[3]		2,067,338
Commercial | Other Commercial | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		1,864,825
Commercial | Other Commercial | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	[2]		2,043,464
Consumer
Financing Receivable, Impaired [Line Items]
Nonaccrual		264
Loans held for investment		378,680
Consumer | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	[1],[2]		20
Loans held for investment			409,567	[2],[3]	$ 398,226
Consumer | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		$ 378,416
Consumer | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	[2]		$ 409,547

[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.

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