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Equity Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, Exercises in Period, Total Intrinsic Value	$ 25.6	$ 42.1	$ 41.4
Performance Contingent Unit Share Payout	1.07	0.75
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	1 year 5 months
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 24.7
Performance Contingent Units Measurement Period	3 years
Allocated Share-based Compensation Expense	$ 30.1	$ 22.3	$ 33.1
Options, Grants in Period, Weighted Average Exercise Price	$ 150.87	$ 129.72	$ 93.53
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	286,874,000
Expiration Period	10 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	164,889,000
Options, Grants in Period, Weighted Average Exercise Price	$ 150.87
Flexible Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Of Shares Available For Grant	14,960,077
Flexible Stock Plan For Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Of Shares Available For Grant	412,500
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	170,080	137,083
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	110,042
Options, Grants in Period, Weighted Average Exercise Price	$ 150.87
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	28,023
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	20,393
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	1 year
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	5 years