Loans and Leases (Details 2) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018		Mar. 31, 2018
Financing Receivable, Impaired [Line Items]
Nonaccrual	$ 88,527	$ 79,333
Loans held for investment	18,307,697	17,957,713
Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual		79,333
Loans held for investment		17,957,713	[1]	$ 16,455,285
Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment	18,219,170
Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment		17,878,380
Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Nonaccrual	15,194
Loans held for investment	8,159,458	7,918,141
Real Estate Mortgage | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual		17,845
Loans held for investment		7,918,141		7,554,243
Real Estate Mortgage | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment	8,144,264
Real Estate Mortgage | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment		7,900,296
Real Estate Mortgage | Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	12,750
Loans held for investment	4,640,510	4,824,298
Real Estate Mortgage | Commercial | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual		15,321
Loans held for investment		4,824,298
Real Estate Mortgage | Commercial | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment	4,627,760
Real Estate Mortgage | Commercial | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment		4,808,977
Real Estate Mortgage | Residential Real Estate
Financing Receivable, Impaired [Line Items]
Nonaccrual	2,444
Loans held for investment	3,518,948	3,093,843
Real Estate Mortgage | Residential Real Estate | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual		2,524
Loans held for investment		3,093,843
Real Estate Mortgage | Residential Real Estate | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment	3,516,504
Real Estate Mortgage | Residential Real Estate | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment		3,091,319
Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Nonaccrual	430
Loans held for investment	2,351,724	2,233,656
Real Estate Construction and Land | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual		442
Loans held for investment		2,233,656		1,677,002
Real Estate Construction and Land | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment	2,351,294
Real Estate Construction and Land | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment		2,233,214
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable
Financing Receivable, Impaired [Line Items]
Nonaccrual	430
Loans held for investment	943,596	912,583
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual		442
Loans held for investment		912,583
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment	943,166
Real Estate Construction and Land | Commercial Real Estate Construction Loan Receivable | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment		912,141
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable
Financing Receivable, Impaired [Line Items]
Nonaccrual	0
Loans held for investment	1,408,128	1,321,073
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual		0
Loans held for investment		1,321,073
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment	1,408,128
Real Estate Construction and Land | Residential Real Estate Construction Financing Receivable | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment		1,321,073
Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	72,476
Loans held for investment	7,424,354	7,404,595
Commercial | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual		60,003
Loans held for investment		7,404,595		6,826,123
Commercial | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment	7,351,878
Commercial | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment		7,344,592
Commercial | Asset Based
Financing Receivable, Impaired [Line Items]
Nonaccrual	43,406
Loans held for investment	3,422,202	3,305,421
Commercial | Asset Based | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual		32,324
Loans held for investment		3,305,421
Commercial | Asset Based | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment	3,378,796
Commercial | Asset Based | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment		3,273,097
Commercial | Venture Capital Loans
Financing Receivable, Impaired [Line Items]
Nonaccrual	20,437
Loans held for investment	2,027,450	2,038,748
Commercial | Venture Capital Loans | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual		20,299
Loans held for investment		2,038,748
Commercial | Venture Capital Loans | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment	2,007,013
Commercial | Venture Capital Loans | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment		2,018,449
Commercial | Other Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	8,633
Loans held for investment	1,974,702	2,060,426
Commercial | Other Commercial | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual		7,380
Loans held for investment		2,060,426
Commercial | Other Commercial | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment	1,966,069
Commercial | Other Commercial | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment		2,053,046
Consumer
Financing Receivable, Impaired [Line Items]
Nonaccrual	427
Loans held for investment	372,161	401,321
Consumer | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Nonaccrual		1,043
Loans held for investment		401,321		$ 397,917
Consumer | Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment	$ 371,734
Consumer | Performing | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Impaired [Line Items]
Loans held for investment		$ 400,278

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