Benefit Plans - Changes in Projected Benefit Obligations and Fair Value of Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Changes in projected benefit obligation:
Projected benefit obligation as of the beginning of the period	$ 52,142	$ 27,539
Acquired	0	16,831
Service cost	1,347	910	$ 548
Interest cost	1,642	1,794	1,107
Actuarial loss	7,038	6,688
Benefits paid	(1,690)	(1,620)
Projected benefit obligation as of the end of the period	60,479	52,142	27,539
Changes in fair value of plan assets:
Fair value of plan assets as of the beginning of the period	42,866	20,254
Acquired	0	16,027
Actual return (loss) on plan assets	4,860	6,405
Employer contributions	125	1,800
Benefits paid	(1,690)	(1,620)
Fair value of plan assets as of the end of the period	$ 46,161	$ 42,866	$ 20,254