Summary of Significant Accounting Policies - Allowance for doubtful accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of Significant Accounting Policies
Balance at Beginning of PeriodBalance at Beginning of Period	$ 671	$ 759	$ 727	$ 518
Charged to Costs and Expenses	578	444	333
Allowance From Acquisitions		25	181
Write Off of Uncollectible Accounts, Net of Recoveries	(666)	(437)	(305)
Balance at End of Period	$ 671	$ 759	$ 727	$ 518