Share-Based Compensation Plans Summary of options outstanding and exercisable (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Share options outstanding and share options exercisable
Share options, outstanding (in shares)	3,462
Share options exercisable (in shares)	3,270
$14.71 - $22.86 [Member]
Share options outstanding and share options exercisable
Share options, range of exercise prices, low end of the range (in dollars per share)	$ 14.71
Share options, range of exercise prices, high end of the range (in dollars per share)	$ 22.86
Share options, outstanding (in shares)	1,244
Weighted average remaining contractual life of share options outstanding	1 year 5 months 5 days
Weighted average exercise price of share options outstanding (in dollars per share)	$ 22.45
Share options exercisable (in shares)	1,244
Weighted average remaining contractual life of share options exercisable (in years)	1 year 5 months 5 days
Weighted average exercise price of share options exercisable (in dollars per share)	$ 22.45
$22.87 - $25.51 [Member]
Share options outstanding and share options exercisable
Share options, range of exercise prices, low end of the range (in dollars per share)	$ 22.87
Share options, range of exercise prices, high end of the range (in dollars per share)	$ 25.51
Share options, outstanding (in shares)	174
Weighted average remaining contractual life of share options outstanding	1 year 6 months
Weighted average exercise price of share options outstanding (in dollars per share)	$ 25.44
Share options exercisable (in shares)	174
Weighted average remaining contractual life of share options exercisable (in years)	1 year 6 months
Weighted average exercise price of share options exercisable (in dollars per share)	$ 25.44
$25.52 - $32.53 [Member]
Share options outstanding and share options exercisable
Share options, range of exercise prices, low end of the range (in dollars per share)	$ 25.52
Share options, range of exercise prices, high end of the range (in dollars per share)	$ 32.53
Share options, outstanding (in shares)	304
Weighted average remaining contractual life of share options outstanding	10 months 24 days
Weighted average exercise price of share options outstanding (in dollars per share)	$ 27.41
Share options exercisable (in shares)	304
Weighted average remaining contractual life of share options exercisable (in years)	10 months 24 days
Weighted average exercise price of share options exercisable (in dollars per share)	$ 27.41
$32.54 - $36.88 [Member]
Share options outstanding and share options exercisable
Share options, range of exercise prices, low end of the range (in dollars per share)	$ 32.54
Share options, range of exercise prices, high end of the range (in dollars per share)	$ 36.88
Share options, outstanding (in shares)	392
Weighted average remaining contractual life of share options outstanding	2 years 3 months 26 days
Weighted average exercise price of share options outstanding (in dollars per share)	$ 35.89
Share options exercisable (in shares)	323
Weighted average remaining contractual life of share options exercisable (in years)	2 years 1 month 2 days
Weighted average exercise price of share options exercisable (in dollars per share)	$ 35.77
$36.89 - $43.44 [Member]
Share options outstanding and share options exercisable
Share options, range of exercise prices, low end of the range (in dollars per share)	$ 36.89
Share options, range of exercise prices, high end of the range (in dollars per share)	$ 43.44
Share options, outstanding (in shares)	830
Weighted average remaining contractual life of share options outstanding	2 years 6 months 18 days
Weighted average exercise price of share options outstanding (in dollars per share)	$ 39.49
Share options exercisable (in shares)	760
Weighted average remaining contractual life of share options exercisable (in years)	2 years 3 months 22 days
Weighted average exercise price of share options exercisable (in dollars per share)	$ 39.54
$43.45 - $52.93 [Member]
Share options outstanding and share options exercisable
Share options, range of exercise prices, low end of the range (in dollars per share)	$ 43.45
Share options, range of exercise prices, high end of the range (in dollars per share)	$ 52.93
Share options, outstanding (in shares)	518
Weighted average remaining contractual life of share options outstanding	3 years 6 months
Weighted average exercise price of share options outstanding (in dollars per share)	$ 47.05
Share options exercisable (in shares)	465
Weighted average remaining contractual life of share options exercisable (in years)	3 years 1 month 2 days
Weighted average exercise price of share options exercisable (in dollars per share)	$ 46.38