Loans and Leases - Nonaccrual and Performing Loans and Leases Held for Investment (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Financing Receivable, Impaired [Line Items]
Nonaccrual	$ 66,538	$ 61,174	$ 67,652
Loans held for investment, net	24,352,072	22,941,548	18,979,228
Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Nonaccrual	49,534	39,832	48,907
Loans held for investment, net	12,039,291	11,178,720	7,987,213
Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Nonaccrual	6,215	4,715	718
Loans held for investment, net	3,693,489	3,437,127	3,565,823
Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	10,402	16,213	17,471
Loans held for investment, net	8,114,695	7,868,051	7,085,840
Consumer
Financing Receivable, Impaired [Line Items]
Nonaccrual	387	414	556
Loans held for investment, net	504,597	457,650	$ 340,352
Performing
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	24,285,534	22,880,374
Performing | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	11,989,757	11,138,888
Performing | Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	3,687,274	3,432,412
Performing | Commercial
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	8,104,293	7,851,838
Performing | Consumer
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	504,210	457,236
Asset-based | Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	1,323	1,464
Loans held for investment, net	4,739,220	4,075,477
Asset-based | Performing | Commercial
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	4,737,897	4,074,013
Venture Capital Loans | Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	3,659	2,799
Loans held for investment, net	2,077,339	2,320,593
Venture Capital Loans | Performing | Commercial
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	2,073,680	2,317,794
Other Commercial | Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	5,420	11,950
Loans held for investment, net	1,298,136	1,471,981
Other Commercial | Performing | Commercial
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	1,292,716	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	802,022	832,591
Commercial Real Estate Construction Loan Receivable | Performing | Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	802,022	832,591
Residential Real Estate Construction Financing Receivable | Real Estate Construction and Land
Financing Receivable, Impaired [Line Items]
Nonaccrual	6,215	4,715
Loans held for investment, net	2,891,467	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	2,885,252	2,599,821
Commercial | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Nonaccrual	32,071	27,540
Loans held for investment, net	3,669,741	3,762,299
Commercial | Performing | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	3,637,670	3,734,759
Residential Real Estate [Member] | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Nonaccrual	17,463	12,292
Loans held for investment, net	8,369,550	7,416,421
Residential Real Estate [Member] | Performing | Real Estate Mortgage
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	$ 8,352,087	$ 7,404,129