Commitments and Contingencies (Narratives) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($) claim case	Dec. 31, 2017 USD ($)
Loss contingency
Accrued liability for the outcomes of non-income based tax audits | $	$ 3.2	$ 1.7
Indemnification liability | $	$ 1.6	$ 1.6
Loss Contingencies [Line Items]
Number of cases settled	3
Number of cases appealed	3
Number of pending cases | case	2
Similar Judge
Loss Contingencies [Line Items]
Number of cases settled	2