Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans not covered under loss-share agreements	$ 14,477		$ 36,990
Specific reserve included in allowance for loan losses	173,106	$ 120,185	176,144	$ 52,162
Valuation adjustment to mortgage servicing rights	(13,561)	9,571	11,726
Changes in fair value, gain (loss)	(12,231)	$ 12,709
Impaired Loans, not covered
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Specific reserve included in allowance for loan losses	$ 5,667		$ 12,845