Significant Accounting Policies Deferred Revenue (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Deferred Revenue Arrangement [Line Items]
Deferred Revenue	$ 98,300,000	$ 72,400,000	$ 98,300,000	$ 72,400,000	$ 89,800,000	$ 81,600,000	$ 67,700,000	$ 59,900,000
New contracts sold	15,800,000	11,100,000	42,600,000	32,500,000
Less: reductions for revenue recognized	(7,300,000)	(6,400,000)	(25,900,000)	(20,000,000.0)
Deferred Revenue, Current	35,100,000	30,700,000	35,100,000	30,700,000
Deferred Revenue, Noncurrent	$ 63,200,000	$ 41,700,000	$ 63,200,000	$ 41,700,000