Summary of Significant Accounting Polices and New Accounting Pronouncements - Reclassification of Preferred Dividends (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Additional paid-in capital	[1]		$ 23,381		$ 23,485		$ 23,614
Accumulated deficit		$ (18,199)	(17,768)	[1]	(18,291)	[1]	(18,827)	[1]
Cumulative dividends reclassified	[1]		606		483		360
As previously reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Additional paid-in capital	[1]		23,987		23,968		23,974
Accumulated deficit	[1]		$ (18,374)		$ (18,774)		$ (19,187)

[1] Also reflects the opening balances at January 1, 2015, 2014 and 2013 presented in the consolidated statement of changes in shareholders' equity.