Share-Based Compensation Plans - Summary of the status of the Company's RSUs (Details) (Restricted share units (RSUs) [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Restricted share units (RSUs) [Member]
Non-vested share awards
Non-vested at beginning of period (in shares)	9,759		10,432		9,916
Target PSAs granted (in shares)	2,844		3,714		5,113
Vested (in shares)	(3,732)		(3,945)		(3,958)
Forfeited (in shares)	(490)		(442)		(639)
Non-vested at end of period (in shares)	8,381		9,759		10,432
Weighted Average Fair value
Non-vested at beginning of period (in dollars per share)	$ 51	[1]	$ 44	[1]	$ 42	[1]
Granted (in dollars per share)	$ 84	[1]	$ 62	[1]	$ 46	[1]
Vested (in dollars per share)	$ 49	[1]	$ 44	[1]	$ 42	[1]
Forfeited (in dollars per share)	$ 58	[1]	$ 47	[1]	$ 44	[1]
Non-vested at end of period (in dollars per share)	$ 63	[1]	$ 51	[1]	$ 44	[1]

[1] Represents per share weighted average fair value of award at date of grant.