Subordinated Debentures - Summarized Activities of Subordinated Debentures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Weighted average interest rate at year-end	5.38%	5.37%
Subordinated notes
Debt Instrument [Line Items]
Average balance outstanding	$ 377,037	$ 183,383
Weighted average rate	5.48%	5.82%
Maximum amount outstanding at any month-end during the year	$ 501,511	$ 233,199
Balance outstanding at end of year	$ 501,511	$ 215,145