Share-Based Compensation Plans (Details 2) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding at December 31 (in shares) | shares	1,717
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options outstanding at December 31 (in dollars per share) | $ / shares	$ 70.47
Summary of stock option activity
Exercisable at December 31 (in shares) | shares	848
Exercisable at December 31, Weighted-Average Exercise Price (in dollars per share) | $ / shares	$ 70.20
Outstanding, weighted average remaining contractual term	7 years 4 months
Stock options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding at January 1 (in shares) | shares	1,529
Granted (in shares) | shares	465
Exercised (in shares) | shares	(235)
Forfeited or expired (in shares) | shares	(42)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options outstanding at January 1 (in dollars per share) | $ / shares	$ 66.35
Granted (in dollars per share) | $ / shares	76.43
Exercised (in dollars per share) | $ / shares	55.41
Forfeited or expired (in dollars per share) | $ / shares	$ 70.56
Summary of stock option activity
Vested and expected to vest at December 31 (in shares) | shares	1,649
Vested and expected to vest at December 31, Weighted-Average Exercise Price (in dollars per share) | $ / shares	$ 70.61
Vested and expected to vest at December 31 in years	7 years 5 months
Exercisable at December 31, in years	6 years
Options outstanding at December 31, Aggregate Intrinsic Value | $	$ 26,209
Vested and expected to vest at December 31, Aggregate Intrinsic Value | $	25,320
Exercisable at December 31, Aggregate Intrinsic Value | $	$ 13,689