Description of Business and Significant Accounting Policies - Narrative (Details) $ in Millions	1 Months Ended	9 Months Ended
	Apr. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment	Dec. 31, 2020 USD ($)
Product Information [Line Items]
Number of reportable segments | segment		1
Performance obligation period (in months)	12 months
Recovery credit program, maximum allowed amount	$ 145
Incentive credits		$ 25
Prepayments offsetting accrued health insurance costs		$ 54	$ 49
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		$ 65	$ 58