Derivatives (Details) In Billions, unless otherwise specified	Mar. 31, 2015 USD ($)	Mar. 31, 2015 JPY (¥)	Dec. 31, 2014 USD ($)	Dec. 31, 2014 JPY (¥)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional amount	$ 1.0invest_DerivativeNotionalAmount	¥ 117.8invest_DerivativeNotionalAmount	$ 1.1invest_DerivativeNotionalAmount	¥ 134.2invest_DerivativeNotionalAmount
Collective account values of underlying variable annuities as a percentage of the guarantee value	113.00%	113.00%	113.00%	113.00%

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