Investments (Payables For Collateral On Investments) (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2018	Dec. 31, 2017
Carrying Value Of Payables For Collateral On Investments [Abstract]
Collateral payable for derivative investments	[1]	$ 366	$ 765
Securities pledged under securities lending agreements	[2]	117	222
Securities pledged under repurchase agreements	[3]	149	530
Investments pledged for Federal Home Loan Bank of Indianapolis ('FHLBI')	[4]	3,580	2,900
Total payables for collateral on investments		4,212	4,417
Fair Value Of Related Investments Or Collateral [Abstract]
Collateral payable for derivative investments	[1]	366	765
Securities pledged under securities lending agreements	[2]	113	213
Securities pledged under repurchase agreements	[3]	185	588
Investments pledged for Federal Home Loan Bank of Indianapolis('FHLBI')	[4]	5,413	4,235
Total payables for collateral on investments		$ 6,077	$ 5,801
Percentage of the fair value of domestic securities obtained as collateral under securities lending agreements.		102.00%
Percentage of the fair value of foreign securities obtained as collateral under securities lending agreements.		105.00%
Maximum [Member]
Fair Value Of Related Investments Or Collateral [Abstract]
Percentage of the fair value of securities obtained as collateral under reverse repurchase agreements.		95.00%
Percentage of the fair value of FHLBI securities obtained as collateral under securities pledged for FHLBI for AFS Securities		115.00%
Percentage of the fair value of FHLBI securities obtained as collateral under securities pledged for FHLBI for mortgage loan		175.00%
Minimum [Member]
Fair Value Of Related Investments Or Collateral [Abstract]
Percentage of the fair value of securities obtained as collateral under reverse repurchase agreements.		80.00%
Percentage of the fair value of FHLBI securities obtained as collateral under securities pledged for FHLBI for AFS Securities		105.00%
Percentage of the fair value of FHLBI securities obtained as collateral under securities pledged for FHLBI for mortgage loan		155.00%

[1] We obtain collateral based upon contractual provisions with our counterparties. These agreements take into consideration the counterparties' credit rating as compared to ours, the fair value of the derivative investments and specified thresholds that if exceeded result in the receipt of cash that is typically invested in cash and invested cash. See Note 6 for additional information.

[2] Our pledged securities under securities lending agreements are included in fixed maturity AFS securities on our Consolidated Balance Sheets. We generally obtain collateral in an amount equal to 102% and 105% of the fair value of the domestic and foreign securities, respectively. We value collateral daily and obtain additional collateral when deemed appropriate. The cash received in our securities lending program is typically invested in cash and invested cash or fixed maturity AFS securities.

[3] Our pledged securities under repurchase agreements are included in fixed maturity AFS securities on our Consolidated Balance Sheets. We generally obtain collateral in an amount between 80% to 95% of the fair value of the securities, and our agreements with third parties contain contractual provisions to allow for additional collateral to be obtained when necessary. The cash received in our repurchase program is typically invested in fixed maturity AFS securities.

[4] Our pledged investments for FHLBI are included in fixed maturity AFS securities and mortgage loans on real estate on our Consolidated Balance Sheets. The collateral requirements are generally 105% to 115% of the fair value for fixed maturity AFS securities and 155% to 175% of the fair value for mortgage loans on real estate. The cash received in these transactions is primarily invested in cash and invested cash or fixed maturity AFS securities.