Fair Value Measurements - Measured Under Certain Conditions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Financing Receivable, Impaired [Line Items]
Impaired real estate, partnership entities, and commercial mortgage loans as a percent of total investments		0.00%
Realized investment losses on impaired real estate, partnership entities, and commercial mortgage loans	$ 1	$ 0
Maximum [Member]
Financing Receivable, Impaired [Line Items]
Impaired real estate, partnership entities, and commercial mortgage loans as a percent of total investments	1.00%