Equity AOCI (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 384
Other comprehensive income before reclassifications	649
Amounts reclassified from other comprehensive income	5
Total other comprehensive income (loss)	654		362
Ending balance	1,038
Available-for-Sale Securities [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	934	[1]
Other comprehensive income before reclassifications	649	[1]
Amounts reclassified from other comprehensive income	(1)	[1]
Total other comprehensive income (loss)	648	[1]
Ending balance	1,582	[1]
Accumulated Other Comprehensive Income (Loss), Other [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(550)	[2]
Other comprehensive income before reclassifications	0	[2]
Amounts reclassified from other comprehensive income	6	[2]
Total other comprehensive income (loss)	6	[2]
Ending balance	$ (544)	[2]

[1] The amounts reclassified from AOCI represent the gain or loss recognized in earnings due to a sale of an available-for-sale security or the recognition of a net impairment recognized in earnings.

[2] Primarily represents activity from our defined benefit pension plans.