Fair Value Measurements - Measured Under Certain Conditions (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Realized investment losses on impaired commercial mortgage loans and real estate entities	$ 16	$ 10
Maximum [Member]
Financing Receivable, Impaired [Line Items]
Impaired commercial mortgage loans and real estate entities as a percent of total investments	1.00%	1.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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