Share-Based Compensation Plans (Details 2) (Stock options, USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Stock options
Share Options
Outstanding at beginning of period (in shares)	5,611	9,116
Granted (in shares)	0	0
Exercised (in shares)	(610)	(1,032)
Forfeited and expired (in shares)	(10)	(12)
Outstanding at end of period (in shares)	4,991	8,072
Exercisable at end of period (in shares)	4,579	7,173
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 32	$ 32
Granted (in dollars per share)	$ 0	$ 0
Exercised (in dollars per share)	$ 31	$ 35
Forfeited and expired (in dollars per share)	$ 33	$ 40
Outstanding at end of period (in dollars per share)	$ 32	$ 31
Exercisable at end of period (in dollars per share)	$ 32	$ 30
Weighted average remaining contractual life of share options outstanding (in years)	2 years 6 months	3 years 1 month 6 days