Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Indemnity
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	$ 24
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	10
Indemnity | Mezzanine debt
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	9
Indemnity | Real estate
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	5
Exchange
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	469
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	134
Exchange | Mezzanine debt
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	158
Exchange | Real estate
Contractual commitments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	$ 177