Lines of Credit and Long-Term Debt - Summary of long-term debt (Details) - USD ($) $ in Millions	Sep. 25, 2018	Dec. 31, 2019	Dec. 31, 2018
Notes Payable and Long Term Debt
Total long-term debt at face value		$ 793	$ 779
Current maturities of long-term debt and unamortized discount		(63)	(40)
Long-term debt, less current maturities		730	739
Term loan due 2028
Notes Payable and Long Term Debt
Total long-term debt at face value		$ 691	$ 698
Face amount	$ 700
Proceeds from issuance of debt	$ 220
Effective interest rate (as a percent)		3.42%	4.15%
Adjusted leverage ratio, maximum	50.00%
Minimum net worth base requirement	$ 2,500
Percentage of consolidated net income added to net worth base amount	25.00%
Maximum dividends per year	$ 100
Sum of subsidiary indebtedness and priority indebtedness as a percentage of consolidated tangible net worth, maximum	15.00%
Term loan due 2022
Notes Payable and Long Term Debt
Face amount	$ 500
Foreign subsidiary obligations
Notes Payable and Long Term Debt
Total long-term debt at face value		$ 102	$ 81