Loans and Leases (Details 2) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 155,784	$ 170,599
Loans held for investment, net	16,972,743	15,455,954
Non Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	155,784	170,599
Loans held for investment, net	16,914,707	15,347,530
Non Purchased Credit Impaired Loans and Leases [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	16,758,923	15,176,931
Non Purchased Credit Impaired Loans and Leases [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	278,405	409,645
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	68,913	69,335
Loans held for investment, net	7,798,991	5,617,956
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	7,730,078	5,548,621
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	102,220	117,181
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	65,563	62,454
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] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	5,295,924	4,291,179
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Commercial Real Estate [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	93,795	99,641
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	3,350	6,881
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] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	2,434,154	1,257,442
Non Purchased Credit Impaired Loans and Leases [Member] | Mortgages [Member] | Residential Real Estate [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	8,425	17,540
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	0	364
Loans held for investment, net	1,591,229	962,839
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	1,591,229	962,475
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	0	773
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Commercial Real Estate Construction Loan Receivable [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	0	0
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] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [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, Impaired [Line Items]
Loans held for investment, net	0	409
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	0	364
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] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	822,154	383,637
Non Purchased Credit Impaired Loans and Leases [Member] | Real Estate Construction [Member] | Residential Real Estate Construction Financing Receivable [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	0	364
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	86,851	100,561
Loans held for investment, net	7,114,920	8,391,560
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	7,028,069	8,290,999
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	175,922	291,267
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Asset Based [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	3,174	2,118
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] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	3,008,526	2,606,927
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Asset Based [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	35,305	28,112
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	30,938	32,848
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] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	626,057	659,119
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Equipment Finance Commercial Financing Receivable [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	30,938	32,848
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Venture Capital Loans [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	29,424	11,687
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] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	2,093,287	1,971,469
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Venture Capital Loans [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	49,671	52,646
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member]
Financing Receivable, Impaired [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] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	1,300,199	3,053,484
Non Purchased Credit Impaired Loans and Leases [Member] | Commercial Portfolio Segment [Member] | Cash Flow [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	23,315	53,908
Loans held for investment, net	60,008	177,661
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	20	339
Loans held for investment, net	409,567	375,175
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member] | Performing Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	409,547	374,836
Non Purchased Credit Impaired Loans and Leases [Member] | Consumer Portfolio Segment [Member] | Classified [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	$ 263	$ 424