Fair Value (Carrying amount and estimated fair value of financial instrument assets and liabilities which are not measured at fair value) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financial Assets [Abstract]
Notes receivable for the issuance of common stock	$ 24	$ 21
Mortgage loans	437	401
Financial Liabilities [Abstract]
Short term debt	13	13
Long term debt	2,558	2,557
Carrying Amount [Member]
Financial Assets [Abstract]
Notes receivable for the issuance of common stock	24	21
Mortgage loans	437	401
Financial Liabilities [Abstract]
Premium deposits and annuity contracts	75	100
Short term debt	13	13
Long term debt	2,558	2,557
Estimated Fair Value [Member]
Financial Assets [Abstract]
Notes receivable for the issuance of common stock	24	21
Mortgage loans	449	418
Financial Liabilities [Abstract]
Premium deposits and annuity contracts	76	104
Short term debt	13	13
Long term debt	2,912	3,016
Level 1 [Member] | Estimated Fair Value [Member]
Financial Assets [Abstract]
Notes receivable for the issuance of common stock
Mortgage loans
Financial Liabilities [Abstract]
Premium deposits and annuity contracts
Short term debt
Long term debt
Level 2 [Member] | Estimated Fair Value [Member]
Financial Assets [Abstract]
Notes receivable for the issuance of common stock
Mortgage loans
Financial Liabilities [Abstract]
Premium deposits and annuity contracts
Short term debt	13	13
Long term debt	2,912	3,016
Level 3 [Member] | Estimated Fair Value [Member]
Financial Assets [Abstract]
Notes receivable for the issuance of common stock	24	21
Mortgage loans	449	418
Financial Liabilities [Abstract]
Premium deposits and annuity contracts	76	104
Short term debt
Long term debt