Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 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	$ 17,959			$ 36,990
Specific reserve included in allowance for loan losses	170,038	$ 168,098	$ 172,354	176,144	$ 145,387	$ 52,162
Valuation adjustment to mortgage servicing rights	(13,561)	13,694
Changes in fair value, gain (loss)	(10,425)	$ 10,876
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	$ 8,549			$ 12,845