Significant Accounting Policies Update (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Accounting Policies [Abstract]
Revenue, Remaining Performance Obligation	$ 977
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Percent	93.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Percent	5.00%