Guaranteed Benefit Features - Separate Accounts by Investment Type (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Equity funds
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	$ 1,904	$ 1,723
Bond funds
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	184	185
Balanced funds
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	329	302
Money market funds
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	46	49
Other
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	10	9
Equity securities
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	2,473	2,268
Fixed income securities
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	7,400	8,000
Held for sale | Equity funds
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	150	127
Held for sale | Bond funds
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	18	16
Held for sale | Balanced funds
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	37	31
Held for sale | Money market funds
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	5	4
Held for sale | Other
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	3	3
Held for sale | Equity securities
Fair Value, Separate Account Investment [Line Items]
Equity securities (including mutual funds)	$ 213	$ 181