Loans and Leases (Details 3) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	$ 16,972,743	$ 15,455,954
Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	16,914,707	15,347,530
Non Purchased Credit Impaired Loans and Leases [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	278,405	409,645
Non Purchased Credit Impaired Loans and Leases [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	16,636,302	14,937,885
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	7,798,991	5,617,956
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	102,220	117,181
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	7,696,771	5,500,775
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	5,361,487	4,353,633
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	93,795	99,641
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	5,267,692	4,253,992
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	2,437,504	1,264,323
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	8,425	17,540
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	2,429,079	1,246,783
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	1,591,229	962,839
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	0	773
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	1,591,229	962,066
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	769,075	578,838
Non Purchased Credit Impaired Loans and Leases [Member] | 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	0	409
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	769,075	578,429
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	822,154	384,001
Non Purchased Credit Impaired Loans and Leases [Member] | 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	364
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	822,154	383,637
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	7,114,920	8,391,560
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	175,922	291,267
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	6,938,998	8,100,293
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	3,011,700	2,609,045
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Asset Based [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	35,305	28,112
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Asset Based [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	2,976,395	2,580,933
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	2,122,711	1,983,156
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Venture Capital Loans [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	49,671	52,646
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Venture Capital Loans [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	2,073,040	1,930,510
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	1,323,514	3,107,392
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	60,008	177,661
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	1,263,506	2,929,731
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	656,995	691,967
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	30,938	32,848
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	626,057	659,119
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	409,567	375,175
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member] | Classified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	263	424
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member] | Nonclassified [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, net	$ 409,304	$ 374,751