Accounting Policies and Supplemental Disclosures - Unearned Revenue (Details) - USD ($) $ in Billions	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Unearned revenue		$ 10.2
Unearned revenue, revenue recognized from beginning balance	$ 5.6
Unearned Revenue, Noncurrent		$ 2.0
Remaining performance obligation, contracts exceeding one year	$ 41.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, weighted average remaining life	3 years 3 months 18 days