Share-Based Compensation Share-Based Compensation (Performance Share Assumptions) (Details) - $ / shares		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Exercise Price	[1]	$ 41.97	$ 34.42	$ 22.47
Expected volatility (b)	[2]	34.00%	34.87%	31.30%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	[3]	2.37%	1.50%	0.85%
Expected term in years (e)	[4]	3 years	3 years	2 years 9 months

[1] The weighted-average fair value was based on performance share units granted during the period.

[2] Expected volatility is based on normalized historical volatility of our shares over a preceding period commensurate with the expected term of the option.

[3] From 2017, the risk-free rate for the expected term of the option is based on the U.S. Treasury yield curve in effect at the time of grant. Prior to 2017, the risk free rate was based on the bond yields from the European Central Bank.

[4] For awards subject to service-based vesting, due to the lack of historical exercise and post-vesting termination patterns of the post-Merger employee base, the expected term was estimated using a simplified method for all awards granted in 2018 and 2017 and the expected term was estimated using historical exercise and post-vesting termination patterns for all awards granted in 2016.