Description of Business and Accounting Policies - Unearned Revenue (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Contract with Customer, Liability	$ 10.2	$ 7.9
Contract with Customer, Liability, Revenue Recognized	6.3
Contract with Customer, Liability, Noncurrent	2.0	$ 1.4
Revenue, Remaining Performance Obligation, Amount	$ 29.8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	3 years 3 months 18 days