Share-Based Compensation Plans - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	6 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Jun. 27, 2015
Number of Options
Options outstanding, number of options (in shares)		749	783
Granted (in shares)		439	344
Exercised (in shares)		(31)	(122)
Forfeited or expired (in shares)		(85)	(256)
Options outstanding, number of options (in shares)	783	1,072	749
Options exercisable (in shares)		519
Options expected to vest (in shares)		533
Weighted-Average Exercise Price Per Share
Beginning options outstanding, weighted average exercise price (in dollars per share)		$ 108.40	$ 99.93
Granted (in dollars per share)		70.34	126.67
Exercised (in dollars per share)		24.75	67.68
Forfeited or expired (in dollars per share)		118.47	126.54
Ending options outstanding, weighted average exercise price (in dollars per share)	$ 99.93	94.90	$ 108.40
Options exercisable (in dollars per share)		107.14
Options expected to vest (in dollars per share)		$ 83.63
Weighted- Average Remaining Term in Years		6 years 10 months 24 days	6 years 7 months 6 days
Weighted- Average Remaining Term in Years, Options exercisable		5 years
Weighted- Average Remaining Term in Years, Options expected to vest		8 years 8 months 12 days
Aggregate Intrinsic Value		$ 10.9	$ 5.5
Aggregate Intrinsic Value, Options exercisable		3.8
Aggregate Intrinsic Value, Options expected to vest		6.8
Options exercised, aggregate intrinsic value	$ 6.7	$ 1.7	$ 5.2	$ 20.7