Loans and Leases (Details 1) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Delinquent loans in loan portfolio
30-89 Days Past Due	$ 29,002	$ 6,600
90 or More Days Past Due	9,775	10,700
Total Past Due	38,777
Current	18,434,075
Loans held for investment, net	18,472,852	17,957,713
Non Purchased Credit Impaired Loans and Leases
Delinquent loans in loan portfolio
30-89 Days Past Due		17,085
90 or More Days Past Due		10,723
Total Past Due		27,808
Current		17,929,905
Loans held for investment, net	18,472,852	17,957,713	$ 16,885,192
Real Estate Mortgage
Delinquent loans in loan portfolio
30-89 Days Past Due	8,208
90 or More Days Past Due	7,054
Total Past Due	15,262
Current	8,060,764
Loans held for investment, net	8,076,026	7,918,141
Real Estate Mortgage | Non Purchased Credit Impaired Loans and Leases
Delinquent loans in loan portfolio
30-89 Days Past Due		5,044
90 or More Days Past Due		8,017
Total Past Due		13,061
Current		7,905,080
Loans held for investment, net	8,076,026	7,918,141	7,566,374
Real Estate Mortgage | Commercial
Delinquent loans in loan portfolio
30-89 Days Past Due	4,516
90 or More Days Past Due	6,632
Total Past Due	11,148
Current	4,424,126
Loans held for investment, net	4,435,274	4,824,298
Real Estate Mortgage | Commercial | Non Purchased Credit Impaired Loans and Leases
Delinquent loans in loan portfolio
30-89 Days Past Due		3,487
90 or More Days Past Due		7,541
Total Past Due		11,028
Current		4,813,270
Loans held for investment, net		4,824,298
Real Estate Mortgage | Residential Real Estate
Delinquent loans in loan portfolio
30-89 Days Past Due	3,692
90 or More Days Past Due	422
Total Past Due	4,114
Current	3,636,638
Loans held for investment, net	3,640,752	3,093,843
Real Estate Mortgage | Residential Real Estate | Non Purchased Credit Impaired Loans and Leases
Delinquent loans in loan portfolio
30-89 Days Past Due		1,557
90 or More Days Past Due		476
Total Past Due		2,033
Current		3,091,810
Loans held for investment, net		3,093,843
Real Estate Construction and Land
Delinquent loans in loan portfolio
30-89 Days Past Due	4,672
90 or More Days Past Due	0
Total Past Due	4,672
Current	2,371,458
Loans held for investment, net	2,376,130	2,233,656
Real Estate Construction and Land | Non Purchased Credit Impaired Loans and Leases
Delinquent loans in loan portfolio
30-89 Days Past Due		1,527
90 or More Days Past Due		442
Total Past Due		1,969
Current		2,231,687
Loans held for investment, net	2,376,130	2,233,656	1,874,026
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable
Delinquent loans in loan portfolio
30-89 Days Past Due	0
90 or More Days Past Due	0
Total Past Due	0
Current	972,891
Loans held for investment, net	972,891	912,583
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Non Purchased Credit Impaired Loans and Leases
Delinquent loans in loan portfolio
30-89 Days Past Due		0
90 or More Days Past Due		442
Total Past Due		442
Current		912,141
Loans held for investment, net		912,583
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable
Delinquent loans in loan portfolio
30-89 Days Past Due	4,672
90 or More Days Past Due	0
Total Past Due	4,672
Current	1,398,567
Loans held for investment, net	1,403,239	1,321,073
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Non Purchased Credit Impaired Loans and Leases
Delinquent loans in loan portfolio
30-89 Days Past Due		1,527
90 or More Days Past Due		0
Total Past Due		1,527
Current		1,319,546
Loans held for investment, net		1,321,073
Commercial
Delinquent loans in loan portfolio
30-89 Days Past Due	15,158
90 or More Days Past Due	2,552
Total Past Due	17,710
Current	7,556,604
Loans held for investment, net	7,574,314	7,404,595
Commercial | Non Purchased Credit Impaired Loans and Leases
Delinquent loans in loan portfolio
30-89 Days Past Due		9,933
90 or More Days Past Due		1,931
Total Past Due		11,864
Current		7,392,731
Loans held for investment, net	7,574,314	7,404,595	7,066,112
Commercial | Asset-based
Delinquent loans in loan portfolio
30-89 Days Past Due	12,382
90 or More Days Past Due	1,624
Total Past Due	14,006
Current	3,592,001
Loans held for investment, net	3,606,007	3,305,421
Commercial | Asset-based | Non Purchased Credit Impaired Loans and Leases
Delinquent loans in loan portfolio
30-89 Days Past Due		47
90 or More Days Past Due		646
Total Past Due		693
Current		3,304,728
Loans held for investment, net		3,305,421
Commercial | Venture Capital Loans
Delinquent loans in loan portfolio
30-89 Days Past Due	447
90 or More Days Past Due	0
Total Past Due	447
Current	2,194,296
Loans held for investment, net	2,194,743	2,038,748
Commercial | Venture Capital Loans | Non Purchased Credit Impaired Loans and Leases
Delinquent loans in loan portfolio
30-89 Days Past Due		4,705
90 or More Days Past Due		0
Total Past Due		4,705
Current		2,034,043
Loans held for investment, net		2,038,748
Commercial | Other Commercial
Delinquent loans in loan portfolio
30-89 Days Past Due	2,329
90 or More Days Past Due	928
Total Past Due	3,257
Current	1,770,307
Loans held for investment, net	1,773,564	2,060,426
Commercial | Other Commercial | Non Purchased Credit Impaired Loans and Leases
Delinquent loans in loan portfolio
30-89 Days Past Due		5,181
90 or More Days Past Due		1,285
Total Past Due		6,466
Current		2,053,960
Loans held for investment, net		2,060,426
Consumer
Delinquent loans in loan portfolio
30-89 Days Past Due	964
90 or More Days Past Due	169
Total Past Due	1,133
Current	445,249
Loans held for investment, net		401,321
Consumer | Non Purchased Credit Impaired Loans and Leases
Delinquent loans in loan portfolio
30-89 Days Past Due		581
90 or More Days Past Due		333
Total Past Due		914
Current		400,407
Loans held for investment, net	$ 446,382	$ 401,321	$ 378,680