Account Balances of Variable Annuity Contract with Death or Living Benefit Guarantees Invested in Separate Account Investment Options (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate account investment	$ 4,954	$ 5,352
Balanced funds
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate account investment	3,046	3,304
Equity funds
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate account investment	1,271	1,387
Bond funds
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate account investment	550	576
Money market funds
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate account investment	$ 87	$ 85