Commitments and Contingencies (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
Indemnity
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	$ 20
Description of commitment: contractual commitment to invest in limited partnership investments	Contractual commitments to invest in limited partnership investments, consisting of private equity securities, mezzanine debt securities, and real estate activities.
Indemnity | Private equity
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	$ 8
Indemnity | Mezzanine debt
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	8
Indemnity | Real estate
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	4
Exchange
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	$ 527
Description of commitment: contractual commitment to invest in limited partnership investments	Contractual commitments to invest in limited partnership investments, consisting of private equity securities, mezzanine debt securities, and real estate activities.
Exchange | Private equity
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	$ 124
Exchange | Mezzanine debt
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	208
Exchange | Real estate
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	$ 195