Loans and Leases (Details 1) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Delinquent loans in loan portfolio
30-89 Days Past Due	$ 14,821	$ 9,788
90 or More Days Past Due	12,036	11,085
Total Past Due	26,857	20,873
Current	19,718,448	18,825,999
Loans held for investment, net	19,745,305	18,846,872	$ 18,307,697
Real Estate Mortgage
Delinquent loans in loan portfolio
30-89 Days Past Due	5,906	4,553
90 or More Days Past Due	6,923	6,721
Total Past Due	12,829	11,274
Current	7,996,115	7,961,473
Loans held for investment, net	8,008,944	7,972,747	8,159,458
Real Estate Mortgage | Commercial
Delinquent loans in loan portfolio
30-89 Days Past Due	4,569	2,448
90 or More Days Past Due	6,241	5,919
Total Past Due	10,810	8,367
Current	4,209,839	4,194,320
Loans held for investment, net	4,220,649	4,202,687
Real Estate Mortgage | Residential Real Estate
Delinquent loans in loan portfolio
30-89 Days Past Due	1,337	2,105
90 or More Days Past Due	682	802
Total Past Due	2,019	2,907
Current	3,786,276	3,767,153
Loans held for investment, net	3,788,295	3,770,060
Real Estate Construction and Land
Delinquent loans in loan portfolio
30-89 Days Past Due	241	1,429
90 or More Days Past Due	0	0
Total Past Due	241	1,429
Current	2,880,012	2,736,373
Loans held for investment, net	2,880,253	2,737,802	2,351,724
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable
Delinquent loans in loan portfolio
30-89 Days Past Due	0	0
90 or More Days Past Due	0	0
Total Past Due	0	0
Current	1,087,505	1,082,368
Loans held for investment, net	1,087,505	1,082,368
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable
Delinquent loans in loan portfolio
30-89 Days Past Due	241	1,429
90 or More Days Past Due	0	0
Total Past Due	241	1,429
Current	1,792,507	1,654,005
Loans held for investment, net	1,792,748	1,655,434
Commercial
Delinquent loans in loan portfolio
30-89 Days Past Due	8,156	2,800
90 or More Days Past Due	5,011	4,164
Total Past Due	13,167	6,964
Current	8,413,057	7,688,532
Loans held for investment, net	8,426,224	7,695,496	7,424,354
Commercial | Asset-based
Delinquent loans in loan portfolio
30-89 Days Past Due	0	19
90 or More Days Past Due	0	0
Total Past Due	0	19
Current	3,938,402	3,748,388
Loans held for investment, net	3,938,402	3,748,407
Commercial | Venture Capital Loans
Delinquent loans in loan portfolio
30-89 Days Past Due	3,272	0
90 or More Days Past Due	2,989	0
Total Past Due	6,261	0
Current	2,709,576	2,179,422
Loans held for investment, net	2,715,837	2,179,422
Commercial | Other Commercial
Delinquent loans in loan portfolio
30-89 Days Past Due	4,884	2,781
90 or More Days Past Due	2,022	4,164
Total Past Due	6,906	6,945
Current	1,765,079	1,760,722
Loans held for investment, net	1,771,985	1,767,667
Consumer
Delinquent loans in loan portfolio
30-89 Days Past Due	518	1,006
90 or More Days Past Due	102	200
Total Past Due	620	1,206
Current	429,264	439,621
Loans held for investment, net	$ 429,884	$ 440,827	$ 372,161