Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	$ 1,272	$ 2,400
OCI before reclassifications	(70)	(1,144)
Amounts reclassified from AOCI	33	(21)
Balance, end of period	1,235	1,235
Unrealized Investment Gains (Losses), Net of Related Offsets [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	1,285	2,291
OCI before reclassifications	(88)	(1,043)
Amounts reclassified from AOCI	36	(15)
Balance, end of period	1,233	1,233
Unrealized Gains (Losses) on Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	95	158
OCI before reclassifications	(39)	(99)
Amounts reclassified from AOCI	(3)	(6)
Balance, end of period	53	53
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(108)	(49)
OCI before reclassifications	57	(2)
Amounts reclassified from AOCI	0	0
Balance, end of period	$ (51)	$ (51)