Revenue from Contracts with Customers Deferred Service Fees (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2018	Sep. 30, 2018
Deferred Service Fees [Abstract]
Contracts with Customers, Performance Obligation Satisfied within One Year	35.90%
Deferred Revenue, Revenue Recognized		$ 12.7