Loans and Leases (Details 2) - USD ($) $ in Thousands	Jun. 30, 2017		Dec. 31, 2016	Jun. 30, 2016
Financing Receivable, Impaired [Line Items]
Nonaccrual	$ 172,576	[1]	$ 170,599
Loans held for investment	15,543,457		15,455,954
Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	172,576	[2]	170,599
Loans held for investment	15,471,031	[2],[3]	15,347,530	$ 14,504,580
Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	15,298,455	[2]	15,176,931
Real Estate Mortgage | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	70,828	[1]	69,335
Loans held for investment	6,071,798	[2],[3]	5,617,956	5,563,380
Real Estate Mortgage | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	6,000,970	[2]	5,548,621
Real Estate Mortgage | Commercial real estate | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	65,599	[2]	62,454
Loans held for investment	4,387,696	[3]	4,353,633
Real Estate Mortgage | Commercial real estate | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	4,322,097	[2]	4,291,179
Real Estate Mortgage | Residential Real Estate | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	5,229	[2]	6,881
Loans held for investment	1,684,102	[3]	1,264,323
Real Estate Mortgage | Residential Real Estate | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	1,678,873	[2]	1,257,442
Real Estate Construction and Land | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	0	[1]	364
Loans held for investment	1,163,340	[2],[3]	962,839	696,233
Real Estate Construction and Land | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	1,163,340	[2]	962,475
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	0	[2]	0
Loans held for investment	690,058	[3]	578,838
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	690,058	[2]	578,838
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	0	[2]	364
Loans held for investment	473,282	[3]	384,001
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	473,282	[2]	383,637
Commercial | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	101,276	[1]	100,561
Loans held for investment	7,837,667	[2],[3]	8,391,560	8,032,333
Commercial | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	7,736,391	[2]	8,290,999
Commercial | Cash Flow | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	43,169	[2]	53,908
Loans held for investment	2,830,612	[3]	3,107,392
Commercial | Cash Flow | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	2,787,443	[2]	3,053,484
Commercial | Asset Based | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	1,718	[2]	2,118
Loans held for investment	2,392,124	[3]	2,609,045
Commercial | Asset Based | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	2,390,406	[2]	2,606,927
Commercial | Venture Capital Loans | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	25,278	[2]	11,687
Loans held for investment	2,001,381	[3]	1,983,156
Commercial | Venture Capital Loans | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	1,976,103	[2]	1,971,469
Commercial | Equipment Finance Commercial Financing Receivable | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	31,111	[2]	32,848
Loans held for investment	613,550	[3]	691,967
Commercial | Equipment Finance Commercial Financing Receivable | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	582,439	[2]	659,119
Consumer | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual	472	[1]	339
Loans held for investment	398,226	[3]	375,175	$ 212,634
Consumer | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment	$ 397,754	[2]	$ 374,836

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

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

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