Loans and Leases (Details 3) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		$ 17,957,713	$ 16,972,743
Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		237,110	278,405	[1]
Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		261,398	302,168	[1]
Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		17,459,205	16,334,134	[1]
Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		7,918,141	7,798,991	[1]
Mortgages [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		68,255	102,220	[1]
Mortgages [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		75,753	127,070	[1]
Mortgages [Member] | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		7,774,133	7,569,701	[1]
Mortgages [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		4,824,298	5,361,487	[1]
Mortgages [Member] | Commercial Real Estate [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		57,734	93,795	[1]
Mortgages [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		74,785	122,488	[1]
Mortgages [Member] | Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		4,691,779	5,145,204	[1]
Mortgages [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		3,093,843	2,437,504	[1]
Mortgages [Member] | Residential Real Estate [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		10,521	8,425	[1]
Mortgages [Member] | Residential Real Estate [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		968	4,582	[1]
Mortgages [Member] | Residential Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		3,082,354	2,424,497	[1]
Real Estate Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		2,233,656	1,591,229	[1]
Real Estate Construction [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		442	0	[1]
Real Estate Construction [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		8,568	619	[1]
Real Estate Construction [Member] | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		2,224,646	1,590,610	[1]
Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		912,583	769,075	[1]
Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		442	0	[1]
Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		7,041	0	[1]
Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member] | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		905,100	769,075	[1]
Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		1,321,073	822,154	[1]
Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		0	0	[1]
Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		1,527	619	[1]
Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member] | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		1,319,546	821,535	[1]
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		7,404,595	7,114,920	[1]
Commercial Portfolio Segment [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		167,214	175,922	[1]
Commercial Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		176,062	173,349	[1]
Commercial Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		7,061,319	6,765,649	[1]
Commercial Portfolio Segment [Member] | Asset Based [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		3,305,421	2,924,871	[1]
Commercial Portfolio Segment [Member] | Asset Based [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		45,957	51,000	[1]
Commercial Portfolio Segment [Member] | Asset Based [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		48,338	37,256	[1]
Commercial Portfolio Segment [Member] | Asset Based [Member] | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		3,211,126	2,836,615	[1]
Commercial Portfolio Segment [Member] | Venture Capital Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		2,038,748	2,122,711	[1]
Commercial Portfolio Segment [Member] | Venture Capital Loans [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		28,731	49,671	[1]
Commercial Portfolio Segment [Member] | Venture Capital Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		77,588	114,210	[1]
Commercial Portfolio Segment [Member] | Venture Capital Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		1,932,429	1,958,830	[1]
Commercial Portfolio Segment [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		2,060,426	2,067,338	[1]
Commercial Portfolio Segment [Member] | Other Commercial [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		92,526	75,251	[1]
Commercial Portfolio Segment [Member] | Other Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		50,136	21,883	[1]
Commercial Portfolio Segment [Member] | Other Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		1,917,764	1,970,204	[1]
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		401,321	409,567	[1]
Consumer Portfolio Segment [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		1,199	263	[1]
Consumer Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		1,015	1,130	[1]
Consumer Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net		$ 399,107	408,174	[1]
Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	[2],[3]		16,914,707
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	[2],[3]		7,798,991
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	[2],[3]		5,361,487
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	[2],[3]		2,437,504
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	[2],[3]		1,591,229
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	[2],[3]		769,075
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	[2],[3]		822,154
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	[2],[3]		7,114,920
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Asset Based [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	[2],[3]		2,924,871
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Venture Capital Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	[2],[3]		2,122,711
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	[2],[3]		2,067,338
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	[2],[3]		$ 409,567

[1] Excludes PCI loans.

[2] Excludes PCI loans.

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