Goodwill and Other Intangible Assets - Goodwill and Other Intangibles (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Total	$ 107,091	$ 111,110
Core deposit intangible
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	144,202	146,355
Accumulated amortization	(50,514)	(48,992)
Total	93,688	97,363	$ 111,808
Books of Business Intangible
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	19,937	19,937
Accumulated amortization	(6,534)	(6,190)
Total	$ 13,403	$ 13,747	$ 15,532