Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Indemnity
Contractual commitments to invest in limited partnership investments
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 to invest in limited partnership investments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	10
Indemnity | Mezzanine debt
Contractual commitments to invest in limited partnership investments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	9
Indemnity | Real estate
Contractual commitments to invest in limited partnership investments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	5
Exchange
Contractual commitments to invest in limited partnership investments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	459
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 to invest in limited partnership investments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	141
Exchange | Mezzanine debt
Contractual commitments to invest in limited partnership investments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	156
Exchange | Real estate
Contractual commitments to invest in limited partnership investments
Represents the entity's maximum contractual commitments to invest in its limited partnership investments	$ 162