Investments and Derivative Instruments Investments and Derivative Instruments (Details 20) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2012 Other Investments [Member]		Jun. 30, 2012 Other Investments [Member]		Jun. 30, 2013 Other Liabilities [Member]		Dec. 31, 2012 Other Liabilities [Member]
Offsetting Assets [Line Items]
Derivative Liability, Fair Value, Gross Asset							$ (2,141)		$ (2,113)
Derivative Asset, Fair Value, Gross Asset	2,783	4,489	2,732		1,809
Derivative Asset, Fair Value, Gross Liability			2,238		1,457
Derivative Assets			581	[1]	320	[1]
Derivative, Collateral, Obligation to Return Cash			(87)	[2]	32	[2]
Derivative Asset, Fair Value of Collateral			490	[3]	241	[3]
Derivative Asset, Fair Value, Amount Offset Against Collateral			4		111
Derivative Liability, Fair Value, Gross Liability	4,529	5,937					(1,498)		(1,759)
Derivative Liabilities							(652)	[4]	38	[4]
Derivative, Collateral, Right to Reclaim Cash							9	[4]	(392)	[4]
Derivative Liability, Fair Value of Collateral							(570)	[3]	(300)	[3]
Derivative Liability, Fair Value, Amount Offset Against Collateral							$ (73.0)		$ (54.0)

[1] Included in other invested assets in the Company's Condensed Consolidated Balance Sheets.

[2] Included in other assets in the Company's Condensed Consolidated Balance Sheets.

[3] Excludes exchange-traded futures which are settled daily.

[4] Included in other liabilities in the Company's Condensed Consolidated Balance Sheets.