Fair Value Disclosures (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Assets
Investments in debt and equity securities	$ 1,362	$ 1,367
Recurring basis
Assets
Investments in debt and equity securities	1,274	1,288
Total Assets	1,362	1,367
Liabilities
Derivative Liabilities, at Fair Value, Net	21	72
Total Liabilities	21	72
U.S. treasury bonds
Assets
Investments in debt and equity securities	9	9
U.S. treasury bonds | Recurring basis
Assets
Investments in debt and equity securities	9	9
Other U.S. and non-U.S. government bonds
Assets
Investments in debt and equity securities	58	60
Other U.S. and non-U.S. government bonds | Recurring basis
Assets
Investments in debt and equity securities	58	60
Corporate bonds
Assets
Investments in debt and equity securities	482	492
Corporate bonds | Recurring basis
Assets
Investments in debt and equity securities	482	492
Asset-backed securities
Assets
Investments in debt and equity securities	88	90
Asset-backed securities | Recurring basis
Assets
Investments in debt and equity securities	88	90
U.S. governmental agency | Recurring basis
Assets
Investments in debt and equity securities	212	223
Residential
Assets
Investments in debt and equity securities	9	10
Residential | Recurring basis
Assets
Investments in debt and equity securities	9	10
Commercial
Assets
Investments in debt and equity securities	31	36
Commercial | Recurring basis
Assets
Investments in debt and equity securities	31	36
Large capitalization value
Assets
Investments in debt and equity securities	325	312
Large capitalization value | Recurring basis
Assets
Investments in debt and equity securities	325	312
Smaller company growth
Assets
Investments in debt and equity securities	60	56
Smaller company growth | Recurring basis
Assets
Investments in debt and equity securities	60	56
REIT
Assets
Investments in debt and equity securities	88	79
REIT | Recurring basis
Assets
Investments in debt and equity securities	88	79
Level 1 | Recurring basis
Assets
Investments in debt and equity securities	394	377
Total Assets	394	377
Liabilities
Derivative Liabilities, at Fair Value, Net	0	0
Total Liabilities	0	0
Level 1 | U.S. treasury bonds | Recurring basis
Assets
Investments in debt and equity securities	9	9
Level 1 | Other U.S. and non-U.S. government bonds | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 1 | Corporate bonds | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 1 | Asset-backed securities | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 1 | U.S. governmental agency | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 1 | Residential | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 1 | Commercial | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 1 | Large capitalization value | Recurring basis
Assets
Investments in debt and equity securities	325	312
Level 1 | Smaller company growth | Recurring basis
Assets
Investments in debt and equity securities	60	56
Level 1 | REIT | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 2 | Recurring basis
Assets
Investments in debt and equity securities	880	911
Total Assets	880	911
Liabilities
Derivative Liabilities, at Fair Value, Net	21	72
Total Liabilities	21	72
Level 2 | U.S. treasury bonds | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 2 | Other U.S. and non-U.S. government bonds | Recurring basis
Assets
Investments in debt and equity securities	58	60
Level 2 | Corporate bonds | Recurring basis
Assets
Investments in debt and equity securities	482	492
Level 2 | Asset-backed securities | Recurring basis
Assets
Investments in debt and equity securities	88	90
Level 2 | U.S. governmental agency | Recurring basis
Assets
Investments in debt and equity securities	212	223
Level 2 | Residential | Recurring basis
Assets
Investments in debt and equity securities	9	10
Level 2 | Commercial | Recurring basis
Assets
Investments in debt and equity securities	31	36
Level 2 | Large capitalization value | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 2 | Smaller company growth | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 2 | REIT | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 3 | Recurring basis
Assets
Investments in debt and equity securities	0	0
Total Assets	88	79
Liabilities
Derivative Liabilities, at Fair Value, Net	0	0
Total Liabilities	0	0
Level 3 | U.S. treasury bonds | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 3 | Other U.S. and non-U.S. government bonds | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 3 | Corporate bonds | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 3 | Asset-backed securities | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 3 | U.S. governmental agency | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 3 | Residential | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 3 | Commercial | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 3 | Large capitalization value | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 3 | Smaller company growth | Recurring basis
Assets
Investments in debt and equity securities	0	0
Level 3 | REIT | Recurring basis
Assets
Investments in debt and equity securities	$ 88	$ 79