Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Loan Portfolio Held for Investment (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Loan Portfolio [Abstract]
Total LHFI	$ 10,944,840		$ 10,247,829
Less ACL, LHFI	103,140	$ 98,734	99,457	$ 104,032	$ 109,191	$ 117,306
Net LHFI	10,841,700		10,148,372
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	664,817		596,968
Other Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	540,950		517,683
Secured by 1-4 Family Residential Properties [Member] | Other Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	1,884,012		1,460,310
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	555,311		726,043
Other Construction [Member] | Other Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	775,241		711,813
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	3,178,079		2,977,084
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	1,551,001		1,414,279
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	164,001		162,555
State and Other Political Subdivision Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	1,110,795		1,146,251
Other Commercial Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	$ 520,633		$ 534,843