Stock-Based Compensation (Details) - Summary Of Changes In SARs Outstanding - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Weighted Average Remaining Contractual Term (Years)
Remaining weighted average service period	2 years 4 months 24 days
Stock Appreciation Rights (SARs)
SARs
Outstanding at December 31, 2016 (in shares)	1.3
Granted (in shares)	0.3
Forfeited (in shares)	(0.1)
Exercised (in shares)	(0.3)
Outstanding at December 31, 2017 (in shares)	1.2	1.3
Vested and exercisable at December 31, 2017 (in shares)	0.5
Per Share Weighted Average Exercise Price
Outstanding at December 31, 2016 (in Dollars per share)	$ 66.22
Granted (in Dollars per share)	99.07
Forfeited (in Dollars per share)	85.28
Exercised (in Dollars per share)	52.72
Outstanding at December 31, 2017 (in Dollars per share)	76.73	$ 66.22
Vested and exercisable at December 31, 2017 (in Dollars per share)	65.67
Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2016 (in Dollars per share)	15.77
Granted (in Dollars per share)	22.02
Forfeited (in Dollars per share)	10.49
Exercised (in Dollars per share)	14.85
Outstanding at December 31, 2017 (in Dollars per share)	17.35	$ 15.77
Vested and exercisable at December 31, 2017 (in Dollars per share)	$ 15.69
Weighted Average Remaining Contractual Term (Years)
Weighted average remaining contractual terms	4 years 3 months 11 days	4 years 4 months 24 days
Remaining weighted average service period	6 years 1 month 6 days
Weighted average remaining contractual terms vested and exercisable	3 years 2 months 19 days