Share-Based Compensation Plans - RTSR fair value assumptions (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield		0.80%	0.90%
Volatility, as a percent		31.20%	30.00%
Risk-free interest rate		2.80%	1.80%
Expected life in years		5 years 7 months 6 days	5 years 4 months 24 days
RTSR
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	1.60%	0.90%	0.90%
Volatility, as a percent	40.20%	35.30%	36.10%
Risk-free interest rate	1.90%	2.40%	1.40%
Expected life in years	2 years 4 months 24 days	2 years 9 months 18 days	2 years 7 months 6 days