Loans and Leases - Nonaccrual and Performing Loans and Leases Held for Investment (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021
Financing Receivable, Impaired [Line Items]
Nonaccrual	$ 89,742	$ 61,174	$ 64,507
Loans held for investment, net	27,660,041	22,941,548	20,511,020
Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Nonaccrual	68,722	39,832	33,162
Loans held for investment, net	14,630,749	11,178,720	9,580,957
Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Nonaccrual	7,101	4,715	19,918
Loans held for investment, net	4,293,516	3,437,127	3,651,873
Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	13,552	16,213	10,932
Loans held for investment, net	8,271,182	7,868,051	6,872,222
Consumer
Financing Receivable, Impaired [Line Items]
Nonaccrual	367	414	495
Loans held for investment, net	464,594	457,650	$ 405,968
Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	27,570,299	22,880,374
Performing | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	14,562,027	11,138,888
Performing | Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	4,286,415	3,432,412
Performing | Commercial
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	8,257,630	7,851,838
Performing | Consumer
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	464,227	457,236
Asset-based | Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	2,127	1,464
Loans held for investment, net	5,154,654	4,075,477
Asset-based | Performing | Commercial
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	5,152,527	4,074,013
Venture Capital Loans | Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	3,809	2,799
Loans held for investment, net	2,001,086	2,320,593
Venture Capital Loans | Performing | Commercial
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	1,997,277	2,317,794
Other Commercial | Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	7,616	11,950
Loans held for investment, net	1,115,442	1,471,981
Other Commercial | Performing | Commercial
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	1,107,826	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	843,086	832,591
Commercial Real Estate Construction Loan Receivable | Performing | Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	843,086	832,591
Residential Real Estate Construction Financing Receivable | Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Nonaccrual	7,101	4,715
Loans held for investment, net	3,450,430	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	3,443,329	2,599,821
Commercial | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Nonaccrual	42,772	27,540
Loans held for investment, net	3,770,706	3,762,299
Commercial | Performing | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	3,727,934	3,734,759
Residential Real Estate [Member] | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Nonaccrual	25,950	12,292
Loans held for investment, net	10,860,043	7,416,421
Residential Real Estate [Member] | Performing | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	$ 10,834,093	$ 7,404,129