Loans and Leases - Credit Risk Rating Categories for Loans and Leases Held for Investment (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	$ 24,352,072	$ 22,941,548	$ 18,979,228
Real Estate Mortgage
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	12,039,291	11,178,720	7,987,213
Real Estate Construction and Land
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,693,489	3,437,127	3,565,823
Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	8,114,695	7,868,051	7,085,840
Consumer
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	504,597	457,650	$ 340,352
Classified
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	82,068	116,104
Classified | Real Estate Mortgage
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	58,307	79,906
Classified | Real Estate Construction and Land
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	6,215	4,715
Classified | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	17,082	31,044
Classified | Consumer
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	464	439
Special Mention
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	377,315	391,611
Special Mention | Real Estate Mortgage
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	181,690	211,657
Special Mention | Real Estate Construction and Land
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	84,644	69,447
Special Mention | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	108,364	108,666
Special Mention | Consumer
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	2,617	1,841
Pass
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	23,892,689	22,433,833
Pass | Real Estate Mortgage
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	11,799,294	10,887,157
Pass | Real Estate Construction and Land
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,602,630	3,362,965
Pass | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	7,989,249	7,728,341
Pass | Consumer
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	501,516	455,370
Asset-based | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	4,739,220	4,075,477
Asset-based | Classified | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	4,449	4,591
Asset-based | Special Mention | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	60,367	78,305
Asset-based | Pass | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	4,674,404	3,992,581
Venture Capital Loans | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	2,077,339	2,320,593
Venture Capital Loans | Classified | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,722	4,794
Venture Capital Loans | Special Mention | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	37,083	14,833
Venture Capital Loans | Pass | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	2,036,534	2,300,966
Other Commercial | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	1,298,136	1,471,981
Other Commercial | Classified | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	8,911	21,659
Other Commercial | Special Mention | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	10,914	15,528
Other Commercial | Pass | Commercial
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	1,278,311	1,434,794
Commercial Real Estate Construction Loan Receivable | Real Estate Construction and Land
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	802,022	832,591
Commercial Real Estate Construction Loan Receivable | Classified | Real Estate Construction and Land
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	0	0
Commercial Real Estate Construction Loan Receivable | Special Mention | Real Estate Construction and Land
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	68,864	67,727
Commercial Real Estate Construction Loan Receivable | Pass | Real Estate Construction and Land
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	733,158	764,864
Residential Real Estate Construction Financing Receivable | Real Estate Construction and Land
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	2,891,467	2,604,536
Residential Real Estate Construction Financing Receivable | Classified | Real Estate Construction and Land
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	6,215	4,715
Residential Real Estate Construction Financing Receivable | Special Mention | Real Estate Construction and Land
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	15,780	1,720
Residential Real Estate Construction Financing Receivable | Pass | Real Estate Construction and Land
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	2,869,472	2,598,101
Commercial | Real Estate Mortgage
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,669,741	3,762,299
Commercial | Classified | Real Estate Mortgage
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	35,463	62,206
Commercial | Special Mention | Real Estate Mortgage
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	168,240	191,809
Commercial | Pass | Real Estate Mortgage
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	3,466,038	3,508,284
Residential Real Estate [Member] | Real Estate Mortgage
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	8,369,550	7,416,421
Residential Real Estate [Member] | Classified | Real Estate Mortgage
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	22,844	17,700
Residential Real Estate [Member] | Special Mention | Real Estate Mortgage
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	13,450	19,848
Residential Real Estate [Member] | Pass | Real Estate Mortgage
Financing Receivable, Past Due [Line Items]
Loans held for investment, net	$ 8,333,256	7,378,873
Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Past Due [Line Items]
Loans held for investment, net		$ 22,941,548