Loans and Leases - Nonaccrual and Performing Loans and Leases Held for Investment (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021
Financing Receivable, Impaired [Line Items]
Nonaccrual	$ 78,527	$ 61,174	$ 56,803
Loans held for investment, net	26,501,137	22,941,548	19,506,257
Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Nonaccrual	56,053	39,832	38,198
Loans held for investment, net	13,549,646	11,178,720	8,413,020
Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Nonaccrual	13,287	4,715	2,218
Loans held for investment, net	3,991,039	3,437,127	3,505,584
Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	8,964	16,213	16,027
Loans held for investment, net	8,476,806	7,868,051	7,222,244
Consumer
Financing Receivable, Impaired [Line Items]
Nonaccrual	223	414	360
Loans held for investment, net	483,646	457,650	$ 365,409
Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	26,422,610	22,880,374
Performing | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	13,493,593	11,138,888
Performing | Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	3,977,752	3,432,412
Performing | Commercial
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	8,467,842	7,851,838
Performing | Consumer
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	483,423	457,236
Asset-based | Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	1,189	1,464
Loans held for investment, net	5,068,112	4,075,477
Asset-based | Performing | Commercial
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	5,066,923	4,074,013
Venture Capital Loans | Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	3,120	2,799
Loans held for investment, net	2,179,190	2,320,593
Venture Capital Loans | Performing | Commercial
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	2,176,070	2,317,794
Other Commercial | Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	4,655	11,950
Loans held for investment, net	1,229,504	1,471,981
Other Commercial | Performing | Commercial
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	1,224,849	1,460,031
Commercial Real Estate Construction Loan Receivable | Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Nonaccrual	0	0
Loans held for investment, net	837,423	832,591
Commercial Real Estate Construction Loan Receivable | Performing | Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	837,423	832,591
Residential Real Estate Construction Financing Receivable | Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Nonaccrual	13,287	4,715
Loans held for investment, net	3,153,616	2,604,536
Residential Real Estate Construction Financing Receivable | Performing | Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	3,140,329	2,599,821
Commercial | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Nonaccrual	28,529	27,540
Loans held for investment, net	3,670,515	3,762,299
Commercial | Performing | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	3,641,986	3,734,759
Residential Real Estate [Member] | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Nonaccrual	27,524	12,292
Loans held for investment, net	9,879,131	7,416,421
Residential Real Estate [Member] | Performing | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	$ 9,851,607	$ 7,404,129