Share-Based Compensation Plans - Share options activity (Details) - Share options [Member] - $ / shares shares in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Share Options
Beginning outstanding (in shares)	837	2,300
Granted (in shares)	0	0
Exercised (in shares)	(138)	(1,293)
Forfeited and expired (in shares)	(4)	(9)
Outstanding at end of period (in shares)	695	998
Exercisable at end of period (in shares)	695	998
Weighted-Average Exercise Price
Beginning outstanding (in dollars per share)	$ 40	$ 32
Granted (in dollars per share)	0	0
Exercised (in dollars per share)	38	26
Forfeited and expired (in dollars per share)	41	36
Outstanding at end of period (in dollars per share)	40	39
Exercisable at end of period (in dollars per share)	$ 40	$ 39