Share-Based Compensation - Schedule of the Transactions of the Company's Stock Options (Details) - Stock Options shares in Millions	3 Months Ended
	Mar. 31, 2018 $ / shares shares
Stock Options
Unexercised options outstanding at the beginning of the period (in shares) | shares	0.6
Options granted (in shares) | shares	0.0
Options exercised (in shares) | shares	0.0
Options forfeited (in shares) | shares	0.0
Unexercised options outstanding at the end of the period (in shares) | shares	0.6
Exercisable at the end of the period (in shares) | shares	0.2
Weighted Average Exercise Price
Unexercised options outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 122.04
Options granted (in dollars per share) | $ / shares	203.22
Options exercised (in dollars per share) | $ / shares	98.69
Options forfeited (in dollars per share) | $ / shares	0.00
Unexercised options outstanding at the end of the period (in dollars per share) | $ / shares	124.49
Exercisable at the end of the period (in dollars per share) | $ / shares	$ 120.03
Weighted Average Remaining Contractual Life
Unexercised options outstanding at the end of the period (in years)	3 years 9 months 12 days
Exercisable at the end of the period (in years)	2 years