Schedule II - Valuation And Qualifying Accounts And Reserves Valuation and Qualifying Accounts and Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	$ 2,450	$ 3,773	$ 5,199
Additions charged to costs and expenses	81	348	785
Deductions and net write-offs	0	(1,671)	(2,211)
Balance at end of period	$ 2,531	$ 2,450	$ 3,773