Loans and Leases (Details 1) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Delinquent loans in loan portfolio
30-89 Days Past Due	$ 3,200	$ 3,000
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	14,200	15,900
Loans held for investment, net	16,972,743	15,455,954
Non Purchased Credit Impaired Loans and Leases [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	48,435	31,569
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	14,165	15,945
Financing Receivable, Recorded Investment, Past Due	62,600	47,514
Current	16,852,107	15,300,016
Loans held for investment, net	16,914,707	15,347,530
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	36,069	14,284
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	11,129	5,302
Financing Receivable, Recorded Investment, Past Due	47,198	19,586
Current	7,751,793	5,598,370
Loans held for investment, net	7,798,991	5,617,956
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	29,070	8,590
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	9,107	3,303
Financing Receivable, Recorded Investment, Past Due	38,177	11,893
Current	5,323,310	4,341,740
Loans held for investment, net	5,361,487	4,353,633
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	6,999	5,694
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	2,022	1,999
Financing Receivable, Recorded Investment, Past Due	9,021	7,693
Current	2,428,483	1,256,630
Loans held for investment, net	2,437,504	1,264,323
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	2,081	364
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Financing Receivable, Recorded Investment, Past Due	2,081	364
Current	1,589,148	962,475
Loans held for investment, net	1,591,229	962,839
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	0	0
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Financing Receivable, Recorded Investment, Past Due	0	0
Current	769,075	578,838
Loans held for investment, net	769,075	578,838
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	2,081	364
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Financing Receivable, Recorded Investment, Past Due	2,081	364
Current	820,073	383,637
Loans held for investment, net	822,154	384,001
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	9,723	16,697
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	3,036	10,643
Financing Receivable, Recorded Investment, Past Due	12,759	27,340
Current	7,102,161	8,364,220
Loans held for investment, net	7,114,920	8,391,560
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	562	224
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Financing Receivable, Recorded Investment, Past Due	562	224
Current	409,005	374,951
Loans held for investment, net	409,567	375,175
Non Purchased Credit Impaired Loans and Leases [Member] | Asset Based [Member] | Commercial Portfolio Segment [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	1,512	1,500
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	2
Financing Receivable, Recorded Investment, Past Due	1,512	1,502
Current	3,010,188	2,607,543
Loans held for investment, net	3,011,700	2,609,045
Non Purchased Credit Impaired Loans and Leases [Member] | Venture Capital Loans [Member] | Commercial Portfolio Segment [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	6,533	13,589
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	760	5,769
Financing Receivable, Recorded Investment, Past Due	7,293	19,358
Current	2,115,418	1,963,798
Loans held for investment, net	2,122,711	1,983,156
Non Purchased Credit Impaired Loans and Leases [Member] | Cash Flow [Member] | Commercial Portfolio Segment [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	1,334	191
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	1,586	1,821
Financing Receivable, Recorded Investment, Past Due	2,920	2,012
Current	1,320,594	3,105,380
Loans held for investment, net	1,323,514	3,107,392
Non Purchased Credit Impaired Loans and Leases [Member] | Equipment Finance Commercial Financing Receivable [Member] | Commercial Portfolio Segment [Member]
Delinquent loans in loan portfolio
30-89 Days Past Due	344	1,417
Loan Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	690	3,051
Financing Receivable, Recorded Investment, Past Due	1,034	4,468
Current	655,961	687,499
Loans held for investment, net	$ 656,995	$ 691,967