Share-Based Compensation (Outstanding and Exercisable Options) (Details)	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, number of options (in options) | shares	4,883,800
Options outstanding, weighted average remaining (in years)	4 years 7 months 6 days
Options outstanding, weighted average exercise price (in dollars per option)	$ 36.35
Options exercisable, number of options (in options) | shares	1,788,900
Options exercisable, weighted average exercise price (in dollars per option)	$ 51.61
$26.00 - $33.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, number of options (in options) | shares	3,061,900
Options outstanding, weighted average remaining (in years)	6 years 4 months 24 days
Options outstanding, weighted average exercise price (in dollars per option)	$ 27.33
Options exercisable, number of options (in options) | shares	0
Options exercisable, weighted average exercise price (in dollars per option)	$ 0.00
$45.00 - $51.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, number of options (in options) | shares	1,277,000
Options outstanding, weighted average remaining (in years)	1 year
Options outstanding, weighted average exercise price (in dollars per option)	$ 49.23
Options exercisable, number of options (in options) | shares	1,244,000
Options exercisable, weighted average exercise price (in dollars per option)	$ 49.33
$55.00 - $57.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, number of options (in options) | shares	544,900
Options outstanding, weighted average remaining (in years)	3 years 2 months 12 days
Options outstanding, weighted average exercise price (in dollars per option)	$ 56.82
Options exercisable, number of options (in options) | shares	544,900
Options exercisable, weighted average exercise price (in dollars per option)	$ 56.82
Minimum | $26.00 - $33.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, exercise price range, lower range limit	26.00
Minimum | $45.00 - $51.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, exercise price range, lower range limit	45.00
Minimum | $55.00 - $57.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, exercise price range, lower range limit	55.00
Maximum | $26.00 - $33.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, exercise price range, upper range limit	33.00
Maximum | $45.00 - $51.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, exercise price range, upper range limit	51.00
Maximum | $55.00 - $57.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, exercise price range, upper range limit	$ 57.00