Description of Business and Significant Accounting Policies - Narrative (Details) $ in Millions		6 Months Ended
	Apr. 20, 2020	Jun. 30, 2020 USD ($) segment	Dec. 31, 2019 USD ($)
Product Information [Line Items]
Number of reportable segments | segment		1
Eligible period for one-time fee reduction program	2 years
Unsatisfied performance obligations		$ 56
Advance collections of unbilled revenues		49
Prepayments offsetting accrued health insurance costs		$ 48	$ 39
Non-US | Revenue | Foreign Sales
Product Information [Line Items]
Percent of concentration risk (less than)		1.00%
Health Care
Product Information [Line Items]
Prepayments offsetting accrued health insurance costs		$ 53	$ 52