Loans and Leases (Details 3) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	$ 19,083,377	$ 18,846,872
Financing Receivable, Nonaccrual	91,163	92,353
Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	7,899,936	7,972,747
Financing Receivable, Nonaccrual	45,557	20,824
Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,360,281	2,737,802
Financing Receivable, Nonaccrual	315	364
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	7,502,905	7,695,496
Financing Receivable, Nonaccrual	44,902	70,672
Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	320,255	440,827
Financing Receivable, Nonaccrual	389	493
Classified [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	265,262	175,912
Classified [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	100,310	42,135
Classified [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	42,558	364
Classified [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	121,932	132,800
Classified [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	462	613
Special Mention [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	721,285	322,956
Special Mention [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	323,846	31,781
Special Mention [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	108,351	1,429
Special Mention [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	286,356	288,534
Special Mention [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	2,732	1,212
Pass [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	18,096,830	18,348,004
Pass [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	7,475,780	7,898,831
Pass [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,209,372	2,736,009
Pass [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	7,094,617	7,274,162
Pass [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	317,061	439,002
Performing Financing Receivable [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	18,992,214	18,754,519
Performing Financing Receivable [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	7,854,379	7,951,923
Performing Financing Receivable [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,359,966	2,737,438
Performing Financing Receivable [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	7,458,003	7,624,824
Performing Financing Receivable [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	319,866	440,334
Asset Based [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,429,283	3,748,407
Financing Receivable, Nonaccrual	2,679	30,162
Asset Based [Member] | Classified [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	27,867	32,223
Asset Based [Member] | Special Mention [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	153,301	38,936
Asset Based [Member] | Pass [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,248,115	3,677,248
Asset Based [Member] | Performing Financing Receivable [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,426,604	3,718,245
Venture Capital Loans [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	1,698,508	2,179,422
Financing Receivable, Nonaccrual	1,980	12,916
Venture Capital Loans [Member] | Classified [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	6,508	35,316
Venture Capital Loans [Member] | Special Mention [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	118,125	74,813
Venture Capital Loans [Member] | Pass [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	1,573,875	2,069,293
Venture Capital Loans [Member] | Performing Financing Receivable [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	1,696,528	2,166,506
Other Commercial [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	2,375,114	1,767,667
Financing Receivable, Nonaccrual	40,243	27,594
Other Commercial [Member] | Classified [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	87,557	65,261
Other Commercial [Member] | Special Mention [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	14,930	174,785
Other Commercial [Member] | Pass [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	2,272,627	1,527,621
Other Commercial [Member] | Performing Financing Receivable [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	2,334,871	1,740,073
Commercial Real Estate Construction Loan Receivable [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	1,117,121	1,082,368
Financing Receivable, Nonaccrual	315	364
Commercial Real Estate Construction Loan Receivable [Member] | Classified [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	42,558	364
Commercial Real Estate Construction Loan Receivable [Member] | Special Mention [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	107,592	0
Commercial Real Estate Construction Loan Receivable [Member] | Pass [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	966,971	1,082,004
Commercial Real Estate Construction Loan Receivable [Member] | Performing Financing Receivable [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	1,116,806	1,082,004
Residential Real Estate Construction Financing Receivable [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	2,243,160	1,655,434
Financing Receivable, Nonaccrual	0	0
Residential Real Estate Construction Financing Receivable [Member] | Classified [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	0	0
Residential Real Estate Construction Financing Receivable [Member] | Special Mention [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	759	1,429
Residential Real Estate Construction Financing Receivable [Member] | Pass [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	2,242,401	1,654,005
Residential Real Estate Construction Financing Receivable [Member] | Performing Financing Receivable [Member] | Real Estate Construction [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	2,243,160	1,655,434
Commercial Real Estate [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	4,096,671	4,202,687
Financing Receivable, Nonaccrual	43,731	18,346
Commercial Real Estate [Member] | Classified [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	91,543	33,535
Commercial Real Estate [Member] | Special Mention [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	262,462	30,070
Commercial Real Estate [Member] | Pass [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,742,666	4,139,082
Commercial Real Estate [Member] | Performing Financing Receivable [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	4,052,940	4,184,341
Residential Real Estate [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,803,265	3,770,060
Financing Receivable, Nonaccrual	1,826	2,478
Residential Real Estate [Member] | Classified [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	8,767	8,600
Residential Real Estate [Member] | Special Mention [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	61,384	1,711
Residential Real Estate [Member] | Pass [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,733,114	3,759,749
Residential Real Estate [Member] | Performing Financing Receivable [Member] | Mortgages [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	$ 3,801,439	$ 3,767,582