Revenue Recognition - Additional Information (Details) $ in Billions	6 Months Ended
	Jun. 30, 2018 USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 6.5
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Length of customer life	30 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, percentage	51.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, timing of satisfaction	1 year 6 months
Minimum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract term	1 year
Average expected contract term	10 years
Amortization period	12 months
Maximum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract term	7 years
Average expected contract term	20 years
Amortization period	60 months