Leases - Balance Sheet Disclosures and Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Leases [Abstract]
Operating lease ROU assets	$ 50,155		$ 50,155		$ 50,743
Operating lease liability	$ 54,239		$ 54,239		$ 59,100
Weighted-average remaining lease term-operating leases (Year)	7 years 6 months		7 years 6 months		8 years 3 months 18 days
Weighted average discount rate-operating leases	3.20%		3.20%		3.20%
Operating lease cost	$ 2,217	$ 1,895	$ 6,565	$ 5,700	$ 5,676
Short-term lease cost	34	34	129		102
Variable lease cost	230	281	826		832
Total lease cost	2,481	2,210	7,520		6,610
Operating cash flows from operating leases	2,435	2,101	10,483		6,283
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 28	$ 6,772	$ 4,827		$ 6,822