Stock-Based Compensation - Summary Of Changes In SARs Outstanding (Details) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Weighted Average Remaining Contractual Term (Years)
Remaining weighted average service period	2 years 4 months 1 day
Stock appreciation rights
SARs
Outstanding, Beginning Balance (in shares)	1.2
Granted (in shares)	0.3
Exercised (in shares)	(0.3)
Outstanding, Ending Balance (in shares)	1.2	1.2
Vested and exercisable, ending balance (in shares)	0.5
Per Share Weighted Average Exercise Price
Outstanding, Beginning Balance (in Dollars per share)	$ 76.73
Granted (in Dollars per share)	114.26
Exercised (in Dollars per share)	60.67
Outstanding, Ending Balance (in Dollars per share)	89.45	$ 76.73
Vested and exercisable, ending balance (in Dollars per share)	75.73
Per Share Weighted Average Grant Date Fair Value
Outstanding, Beginning Balance (in Dollars per share)	17.35
Granted (in Dollars per share)	25.63
Exercised (in Dollars per share)	15.10
Outstanding, Ending Balance (in Dollars per share)	19.88	$ 17.35
Vested and exercisable, ending balance (in Dollars per share)	$ 17.02
Weighted Average Remaining Contractual Term (Years)
Weighted average remaining contractual terms	4 years 4 months	4 years 3 months 10 days
Remaining weighted average service period	6 years 1 month 10 days
Weighted average remaining contractual terms vested and exercisable	3 years 2 months 25 days