Derivatives (Details) In Billions, unless otherwise specified	Sep. 30, 2013 USD ($)	Sep. 30, 2013 JPY (¥)	Dec. 31, 2012 USD ($)	Dec. 31, 2012 JPY (¥)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional amount	$ 2.2	¥ 217.1	$ 2.7	¥ 230.0
Collective account values of underlying variable annuities as a percentage of the guarantee value	98.00%	98.00%	87.00%	87.00%

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant