Significant Accounting Policies Deferred Revenue (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Deferred Revenue Arrangement [Line Items]
Deferred Revenue	$ 72,391,000	$ 55,586,000	$ 72,391,000	$ 55,586,000	$ 67,681,000	$ 59,915,000	$ 52,620,000	$ 45,760,000
New contracts sold	11,119,000	8,054,000	32,504,000	25,226,000
Less: reductions for revenue recognized	(6,409,000)	(5,088,000)	(20,028,000)	(15,400,000)
Deferred Revenue, Current	30,703,000	23,893,000	30,703,000	23,893,000
Deferred Revenue, Noncurrent	$ 41,688,000	$ 31,693,000	$ 41,688,000	$ 31,693,000