Retirement Plans - Changes in Accumulated Other Comprehensive Income Before Tax (Details) - Pension Plans, Defined Benefit - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax [Roll Forward]
Total retirement benefit recognized in accumulated other comprehensive income at beginning of year	$ 7	$ 7
Net actuarial loss (gain)	3	(1)
Translation difference	(1)	1
Other	1	0
Total retirement benefit recognized in accumulated other comprehensive income at end of year	$ 10	$ 7