FDIC-Acquired Loans and Loss Sharing Agreements - Accretable Yield Changes for Acquired Loans (Details) - USD ($)		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
TeamBank
Business Acquisition [Line Items]
Beginning Balance		$ 1,157,000	$ 1,356,000	$ 2,071,000
Accretion		(479,000)	(955,000)	(1,042,000)
Reclassification from nonaccretable difference	[1]	198,000	756,000	327,000
Ending balance		876,000	1,157,000	1,356,000
Change in expected accretable yield		198,000	667,000	312,000
Vantus Bank
Business Acquisition [Line Items]
Beginning Balance		1,123,000	1,432,000	1,850,000
Accretion		(831,000)	(1,006,000)	(1,196,000)
Reclassification from nonaccretable difference	[1]	451,000	697,000	778,000
Ending balance		743,000	1,123,000	1,432,000
Change in expected accretable yield		451,000	480,000	778,000
Sun Security Bank
Business Acquisition [Line Items]
Beginning Balance		1,948,000	2,242,000	2,901,000
Accretion		(1,046,000)	(1,562,000)	(1,667,000)
Reclassification from nonaccretable difference	[1]	493,000	1,268,000	1,008,000
Ending balance		1,395,000	1,948,000	2,242,000
Change in expected accretable yield		493,000	810,000	756,000
InterBank
Business Acquisition [Line Items]
Beginning Balance		8,277,000	4,994,000	5,074,000
Accretion		(6,791,000)	(8,798,000)	(8,349,000)
Reclassification from nonaccretable difference	[1]	2,219,000	12,081,000	8,269,000
Ending balance		3,705,000	8,277,000	4,994,000
Change in expected accretable yield		2,200,000	3,900,000	4,100,000
Valley Bank
Business Acquisition [Line Items]
Beginning Balance		4,578,000	3,063,000	2,695,000
Accretion		(3,005,000)	(4,302,000)	(3,892,000)
Reclassification from nonaccretable difference	[1]	2,764,000	5,817,000	4,260,000
Ending balance		4,337,000	4,578,000	3,063,000
Change in expected accretable yield		$ 2,800,000	$ 2,500,000	$ 3,500,000

[1] Represents increases in estimated cash flows expected to be received from the acquired loan pools, primarily due to lower estimated credit losses. The numbers also include changes in expected accretion of the loan pools for TeamBank, Vantus Bank, Sun Security Bank, InterBank and Valley Bank for the year ended December 31, 2020, totaling $198,000, $451,000, $493,000, $2.2 million and $2.8 million, respectively; TeamBank, Vantus Bank, Sun Security Bank, InterBank and Valley Bank for the year ended December 31, 2019, totaling $667,000, $480,000, $810,000, $3.9 million and $2.5 million, respectively; for TeamBank, Vantus Bank, Sun Security Bank, InterBank and Valley Bank for the year ended December 31, 2018, totaling $312,000, $778,000, $756,000, $4.1 million and $3.5 million, respectively