Summary of Significant Accounting Policies - Allowance for Doubtful Accounts Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Doubtful Accounts Receivable
Balance, beginning of year	$ 3,115	$ 4,149	$ 3,080
Additions to expense	778	462	2,434
Write-offs	(158)	(1,659)	(1,392)
Recoveries			5
Other		163	22
Balance, end of year	$ 3,735	$ 3,115	$ 4,149