Investments and Derivative Instruments Level 4 Repurchase Agreements, Dollar Roll Transactions and Other Collateral Transactions (Details) - USD ($)	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015
Repurchase Agreements, Dollar Roll Transactions and Other Collateral Transactions [Line Items]
Securities Loaned	$ 96,000,000	$ 67,000,000
Securities Held as Collateral, at Fair Value	98,000,000	68,000,000
Interest-bearing Deposit Liabilities, Domestic	2,600,000,000	2,500,000,000
Secured Debt, Dollar Rolls	0
US Treasury Securities [Member]
Repurchase Agreements, Dollar Roll Transactions and Other Collateral Transactions [Line Items]
Available-for-sale Securities Pledged as Collateral	17,000,000	35,000,000
Fixed Maturities [Member]
Repurchase Agreements, Dollar Roll Transactions and Other Collateral Transactions [Line Items]
Available-for-sale Securities Pledged as Collateral	458,000,000	440,000,000
Other Liabilities [Member]
Repurchase Agreements, Dollar Roll Transactions and Other Collateral Transactions [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	$ 452,000,000		$ 445,000,000
Cash [Member]
Repurchase Agreements, Dollar Roll Transactions and Other Collateral Transactions [Line Items]
Available-for-sale Securities Pledged as Collateral		$ 5,000,000