Recent Developments Including Mergers and Acquisitions - Additional Information (Detail)	Jun. 17, 2021 USD ($)	May 20, 2021 USD ($) Location	Jan. 22, 2021 USD ($)	Mar. 05, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Business Combination Separately Recognized Transactions [Line Items]
Total assets					$ 9,405,612,000	$ 9,212,357,000	$ 8,565,758,000
Loans held for investment (net of unearned interest)					6,169,442,000	6,394,506,000
Deposits					8,091,914,000	8,064,704,000
Goodwill					$ 149,922,000	$ 149,922,000	$ 148,604,000
Oklahoma [Member]
Business Combination Separately Recognized Transactions [Line Items]
Sale of Loans			$ 21,000,000
Deposits sold			38,000,000
Oklahoma [Member] | Noninterest Income [Member]
Business Combination Separately Recognized Transactions [Line Items]
Gain on transaction			$ 2,500,000
First National Bank and Trust [Member]
Business Combination Separately Recognized Transactions [Line Items]
Total assets		$ 284,000,000
Loans held for investment (net of unearned interest)		195,000,000
Deposits		256,000,000
Purchase price		21,000,000
Bargain purchase gain		4,800,000
Purchase expenses		4,800,000
Intangibles assets, net		$ 1,700,000
First National Bank and Trust [Member] | Oklahoma [Member]
Business Combination Separately Recognized Transactions [Line Items]
Number of banking locations | Location		2
Subordinated Notes due 2036 [Member] | Private Placement [Member]
Business Combination Separately Recognized Transactions [Line Items]
Aggregate principal amount	$ 60,000,000
Fixed-to-floating rate	3.50%
Debt instrument maturity year	2036
Citizens Bankshares, Inc [Member]
Business Combination Separately Recognized Transactions [Line Items]
Total assets				$ 47,800,000
Loans held for investment (net of unearned interest)				22,900,000
Deposits				45,000,000.0
Purchase price				$ 2,900,000
Date of acquisition				Mar. 05, 2020
Intangibles assets, net				$ 206,000
Goodwill				$ 1,300,000