Fair Value Measurements - The carrying value and fair value of financial instruments (Details) - USD ($) $ in Millions		Sep. 30, 2016	Dec. 31, 2015
Financial assets:
Mortgage loans		$ 1,180	$ 1,067
Policy loans		194	201
Financial liabilities:
Long-term debt		1,300	998
Level 1
Financial assets:
Cash and cash equivalents		1,639	1,220
Mortgage loans		0	0
Policy loans		0	0
Total financial assets not accounted for at fair value		1,639	1,220
Financial liabilities:
Annuity benefits accumulated	[1]	0	0
Long-term debt		0	0
Total financial liabilities not accounted for at fair value		0	0
Level 2
Financial assets:
Cash and cash equivalents		0	0
Mortgage loans		0	0
Policy loans		0	0
Total financial assets not accounted for at fair value		0	0
Financial liabilities:
Annuity benefits accumulated	[1]	0	0
Long-term debt		1,417	1,105
Total financial liabilities not accounted for at fair value		1,417	1,105
Level 3
Financial assets:
Cash and cash equivalents		0	0
Mortgage loans		1,193	1,074
Policy loans		194	201
Total financial assets not accounted for at fair value		1,387	1,275
Financial liabilities:
Annuity benefits accumulated	[1]	29,020	25,488
Long-term debt		21	15
Total financial liabilities not accounted for at fair value		29,041	25,503
Carrying Value
Financial assets:
Cash and cash equivalents		1,639	1,220
Mortgage loans		1,180	1,067
Policy loans		194	201
Total financial assets not accounted for at fair value		3,013	2,488
Financial liabilities:
Annuity benefits accumulated	[1]	29,018	26,422
Long-term debt		1,306	1,000
Total financial liabilities not accounted for at fair value		30,324	27,422
Fair Value
Financial assets:
Cash and cash equivalents		1,639	1,220
Mortgage loans		1,193	1,074
Policy loans		194	201
Total financial assets not accounted for at fair value		3,026	2,495
Financial liabilities:
Annuity benefits accumulated	[1]	29,020	25,488
Long-term debt		1,438	1,120
Total financial liabilities not accounted for at fair value		$ 30,458	$ 26,608

[1] Excludes $204 million and $200 million of life contingent annuities in the payout phase at September 30, 2016 and December 31, 2015, respectively.