Allowance for Credit Losses - Roll Forward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts
Balance, beginning of year	$ 3,449	$ 1,748	$ 1,957
Provision (net of recovery)	440	2,090	907
Amounts written off, net of recoveries	(1)	(389)	(1,116)
Balance, end of year	$ 3,888	$ 3,449	$ 1,748