Stock Incentive Plans Stock Incentive Plans Details 3 (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Based Compensation Payout Target	200.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Based Compensation Payout Target	0.00%
Performance Based Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	88,174	93,216	115,158
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Grants in Period, Weighted Average Grant Date Fair Value	$ 78.11	$ 67.39	$ 71.37
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, Non-Option Equity Instruments, Granted	57,900	86,698	57,600
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Grants in Period, Weighted Average Grant Date Fair Value	$ 76.91	$ 67.54	$ 71.37
Restricted Stock Units (RSUs) and Performance Stock Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense	$ 9.2	$ 13.2	$ 10.3
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures	17,323	44,279	16,395
Percent of Units Expected to Settle in Common Stock	96.00%	94.00%	93.00%
Percent of Units Expected to Settle in Cash	4.00%	6.00%	7.00%
Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount	$ 10.4
Performance Based Units Weighted Average Remaining Service Period	1 year 4 months 24 days

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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