- Summary of the status of the Company's share options and related information (Details) (Share options [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share options [Member]
Share Options
Outstanding at beginning of period (in shares)	3,462	5,611	9,116
Granted (in shares)	0	0	0
Exercised (in shares)	(1,155)	(2,116)	(3,413)
Forfeited and expired (in shares)	(7)	(33)	(92)
Outstanding at end of period (in shares)	2,300	3,462	5,611
Exercisable at end of period (in shares)	2,273	3,270	5,117
Shares available for grant (in shares)	16,333	11,330	17,024
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 32	$ 32	$ 32
Granted (in dollars per share)	$ 0	$ 0	$ 0
Exercised (in dollars per share)	$ 33	$ 32	$ 31
Forfeited and expired (in dollars per share)	$ 37	$ 34	$ 37
Outstanding at end of period (in dollars per share)	$ 32	$ 32	$ 32
Exercisable at end of period (in dollars per share)	$ 32	$ 32	$ 31