Loans and Leases (Details 2) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017		Mar. 31, 2017
Financing Receivable, Impaired [Line Items]
Nonaccrual		$ 103,725	$ 155,784	[1]
Loans held for investment		16,455,285	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]	$ 15,460,354
Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		16,351,560
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		24,341
Loans held for investment		7,554,243
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]	5,886,969
Real Estate Mortgage | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		7,529,902
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		19,116
Loans held for investment		5,033,006
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		5,013,890
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		5,225
Loans held for investment		2,521,237
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		2,516,012
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		0
Loans held for investment		1,677,002
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]	1,108,236
Real Estate Construction and Land | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		1,677,002
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		789,892
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		789,892
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		0
Loans held for investment		887,110
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		887,110
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		79,133
Loans held for investment		6,826,123
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]	8,082,678
Commercial | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		6,746,990
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		32,838
Loans held for investment		2,957,890
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		2,925,052
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		21,861
Loans held for investment		1,920,643
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		1,898,782
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		24,434
Loans held for investment		1,947,590
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		1,923,156
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		251
Loans held for investment		397,917
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]	$ 382,471
Consumer | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment		$ 397,666
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.