Investments - Additional Information (Detail) $ in Millions		1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
		Jun. 30, 2016 USD ($)	Sep. 30, 2016 USD ($) Loan	Jun. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) Loan	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) Loan
Schedule of Investments [Line Items]
Aggregate fair value of securities sold			$ 293		$ 186	$ 833	$ 470
Aggregate fair value of securities sold, percentage of book value			95.00%		93.00%	93.00%	94.00%
Less than 12 months, average fair value percentage below cost for securities in a continuous loss position			2.00%			2.00%
12 months or more, Gross unrealized losses			$ 130			$ 130		$ 239
Investments subject to call provisions			10,260			$ 10,260
Percentage of investment portfolio by which no other industry group exceeded						10.00%
Percentage of stockholders' equity by which no single issuer of fixed maturity securities exceeded						10
Commercial mortgage loans outstanding more than 90 days, interest accruing			0			$ 0		0
Commercial mortgage loans on nonaccrual status, past due less than 90 days			$ 0			$ 0		$ 0
Commercial mortgage loans modified or extended, number of loans | Loan			10			10		21
Commercial mortgage loans modified or extended, carrying value			$ 63			$ 63		$ 110
Number of loans modified to troubled debt restructuring | Loan						1
Troubled debt restructuring, loan			1			$ 1
Commercial mortgage loans, recorded investment			6,032			6,032		6,187
Gain related to early extinguishment of debt	[1]		0		$ (2)	48	$ (2)
Policy loan repurchased		$ 134
Investments in partnerships or similar entities generally considered VIEs			171			171		165
Commercial Mortgage Loan
Schedule of Investments [Line Items]
Commercial mortgage loans, recorded investment			6,032			6,032		6,187
Commercial Mortgage Loan | Maximum
Schedule of Investments [Line Items]
Individually impaired commercial mortgage loans			1			1
More Than 20% Below Cost | Structured Securities
Schedule of Investments [Line Items]
12 months or more, Gross unrealized losses			$ 18			$ 18
12 months or more, stated percentage below cost of securities in unrealized loss position			20.00%			20.00%
12 months or more, unrealized losses on other than temporarily impaired securities, portion recognized in OCI, securities in a loss position			$ 0			$ 0
Floating rate commercial mortgage loans
Schedule of Investments [Line Items]
Commercial mortgage loans, recorded investment			0			0		7
Fixed maturity securities
Schedule of Investments [Line Items]
12 months or more, Gross unrealized losses			100			100		239
Fixed maturity securities | U.S. corporate
Schedule of Investments [Line Items]
12 months or more, Gross unrealized losses			32			32		62
Fixed maturity securities | Less Than 20 Percent Below Cost
Schedule of Investments [Line Items]
12 months or more, Gross unrealized losses			$ 69			$ 69		78
12 months or more, average fair value percentage below cost for securities in a continuous loss position			4.00%			4.00%
12 months or more, stated percentage below cost of securities in unrealized loss position			20.00%			20.00%
Fixed maturity securities | More Than 20% Below Cost
Schedule of Investments [Line Items]
12 months or more, stated percentage below cost of securities in unrealized loss position			20.00%			20.00%
Fixed maturity securities | More Than 20% Below Cost | U.S. corporate
Schedule of Investments [Line Items]
12 months or more, Gross unrealized losses			$ 9			$ 9
Stated percentage below cost of securities in unrealized loss position			20.00%			20.00%
Investment grade
Schedule of Investments [Line Items]
12 months or more, Gross unrealized losses			$ 100			$ 100		135
Investment grade | Less Than 20 Percent Below Cost
Schedule of Investments [Line Items]
Less than 12 months, stated percentage below cost of securities in unrealized loss position			20.00%			20.00%
Investment grade | Fixed maturity securities | Less Than 20 Percent Below Cost
Schedule of Investments [Line Items]
12 months or more, Percentage of total gross unrealized losses for securities in a continuous loss position			65.00%			65.00%
Borrowings related to securitization entities
Schedule of Investments [Line Items]
Settlement of outstanding restricted debt		70
Gain related to early extinguishment of debt		64
Residual Interest Related to Securitization Entities
Schedule of Investments [Line Items]
Realized investment losses related to the write-off of residual interest		$ (64)
Utilities | Fixed maturity securities
Schedule of Investments [Line Items]
Percent of investment portfolio, greater than 10%						14.00%
Utilities | Fixed maturity securities | U.S. corporate
Schedule of Investments [Line Items]
12 months or more, Gross unrealized losses			$ 1			$ 1		1
Finance and insurance | Fixed maturity securities
Schedule of Investments [Line Items]
Percent of investment portfolio, greater than 10%						22.00%
Finance and insurance | Fixed maturity securities | U.S. corporate
Schedule of Investments [Line Items]
12 months or more, Gross unrealized losses			6			$ 6		8
Finance and insurance | Fixed maturity securities | More Than 20% Below Cost | U.S. corporate
Schedule of Investments [Line Items]
12 months or more, Gross unrealized losses			$ 3			$ 3
12 months or more, Percentage of total gross unrealized losses for securities in a continuous loss position			33.00%			33.00%
Consumer-non-cyclical | Fixed maturity securities
Schedule of Investments [Line Items]
Percent of investment portfolio, greater than 10%						14.00%
Consumer-non-cyclical | Fixed maturity securities | U.S. corporate
Schedule of Investments [Line Items]
12 months or more, Gross unrealized losses			$ 0			$ 0		4
Energy | Fixed maturity securities | U.S. corporate
Schedule of Investments [Line Items]
12 months or more, Gross unrealized losses			15			15		28
Energy | Fixed maturity securities | More Than 20% Below Cost | U.S. corporate
Schedule of Investments [Line Items]
12 months or more, Gross unrealized losses			$ 6			$ 6
12 months or more, Percentage of total gross unrealized losses for securities in a continuous loss position			67.00%			67.00%
Industrial
Schedule of Investments [Line Items]
Individually impaired commercial mortgage loans			$ 12			$ 12		14
Impaired loans, unpaid principal balance			15			15		15
Individually impaired loans, charge-offs				$ 2		3		1
Individually impaired loans, interest income								1
Commercial mortgage loans, recorded investment			1,544			1,544		1,562
Office
Schedule of Investments [Line Items]
Individually impaired commercial mortgage loans								5
Impaired loans, unpaid principal balance								6
Individually impaired loans, charge-offs								1
Commercial mortgage loans, recorded investment			1,421			1,421		1,516
Retail
Schedule of Investments [Line Items]
Individually impaired commercial mortgage loans			5			5
Impaired loans, unpaid principal balance			7			7
Individually impaired loans, charge-offs						2
Individually impaired loans, average recorded investment						3
Commercial mortgage loans, recorded investment			$ 2,099			$ 2,099		$ 2,116

[1] For the three and nine months ended September 30, 2015, (gains) losses on the early extinguishment of debt were adjusted for the portion attributable to noncontrolling interests of $(1) million.