Consolidated Statement of Shareholder's Interest (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Shareholder's Interest [Roll Forward]
Balance at beginning of period	$ 9,653	$ 8,896
Net income	364	295
Other comprehensive income/(loss), net of tax	(187)	208
Distributions	(28)	(200)
Balance at end of period	9,802	9,199
Shareholder's Interest [Member]
Shareholder's Interest [Roll Forward]
Balance at beginning of period	5,274	5,274
Net income	0	0
Other comprehensive income/(loss), net of tax	0	0
Distributions	0	0
Balance at end of period	5,274	5,274
Accumulated Other Comprehensive Income/(Loss) (Note10) [Member]
Shareholder's Interest [Roll Forward]
Balance at beginning of period	743	600
Net income	0	0
Other comprehensive income/(loss), net of tax	(187)	208
Distributions	0	0
Balance at end of period	556	808
Retained Earnings [Member]
Shareholder's Interest [Roll Forward]
Balance at beginning of period	3,636	3,022
Net income	364	295
Other comprehensive income/(loss), net of tax	0	0
Distributions	(28)	(200)
Balance at end of period	$ 3,972	$ 3,117