Significant Accounting Policies Deferred Revenue (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Deferred Revenue Arrangement [Line Items]
Deferred Revenue	$ 89,800,000	$ 67,700,000	$ 89,800,000	$ 67,700,000	$ 85,600,000	$ 81,600,000	$ 63,500,000	$ 59,900,000
New contracts sold	13,600,000	11,500,000	26,800,000	21,400,000
Less: reductions for revenue recognized	(9,400,000)	(7,300,000)	(18,600,000)	(13,600,000)
Deferred Revenue, Current	32,400,000	28,800,000	32,400,000	28,800,000
Deferred Revenue, Noncurrent	$ 57,400,000	$ 38,900,000	$ 57,400,000	$ 38,900,000