Goodwill and Other Intangible Assets - Finite-Lived Intangible Assets Roll Forward (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Gross Balance of CDI:
Balance, beginning of year	$ 145,212		$ 145,212	$ 145,212	$ 125,945
Additions due to acquisitions	0	$ 0	0	0	19,267
Balance, end of year	145,212	145,212	145,212	145,212	145,212
Accumulated amortization:
Balance, beginning of year	(67,849)	(63,848)	(50,662)	(59,705)	(42,633)
Amortization	(3,912)	(4,001)	(4,538)	(12,056)	(12,567)
Balance, end of year	(71,761)	(67,849)	(55,200)	(71,761)	(55,200)
Net intangible assets	$ 73,451	$ 77,363	$ 90,012	$ 73,451	$ 90,012	$ 85,500