Derivatives (Details Textual) (USD $)	6 Months Ended
Jun. 30, 2012
Derivatives (Textual) [Abstract]
Notional amount of pay-fixed interest rate swaptions	$ 1,000,000,000
Payments to purchase swaptions	$ 29,000,000
Indexed annuities as a fraction of annuity benefits	approximately one-third

Aggregate notional amount of all interest rate derivatives not designated as hedging instruments. Notional amount refers to the monetary amount specified in the interest rate derivative contract.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Notional Amount

-URI http://asc.fasb.org/extlink&oid=6519104

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5580258-113959

Name:	us-gaap_NotionalAmountOfInterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstruments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant