Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Loan Portfolio Held for Investment (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Loan Portfolio [Abstract]
Total LHFI	$ 10,397,129	$ 10,247,829
Less ACL, LHFI	98,734	99,457	$ 117,306
Net LHFI	10,298,395	10,148,372
Construction, Land Development and Other Land [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	628,331	596,968
Other Secured by 1-4 Family Residential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	513,497	517,683
Secured by 1-4 Family Residential Properties [Member] | Other Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	1,593,501	1,460,310
Other Real Estate Secured [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	715,939	726,043
Other Construction [Member] | Other Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	645,628	711,813
Secured by Nonfarm, Nonresidential Properties [Member] | Loans Secured by Real Estate [Member]
Loan Portfolio [Abstract]
Total LHFI	2,975,039	2,977,084
Commercial and Industrial Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	1,495,060	1,414,279
Consumer Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	157,355	162,555
State and Other Political Subdivision Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	1,215,023	1,146,251
Other Commercial Loans [Member]
Loan Portfolio [Abstract]
Total LHFI	$ 457,756	$ 534,843