Dividend restrictions (Details)	12 Months Ended
Dec. 31, 2011
Dividend restrictions [Abstract]
Dividend restrictions	The maximum amount of dividends that the insurance subsidiaries may pay in any twelve-month period without regulatory approval by the Office of the Commissioner of Insurance of the State of Wisconsin is the lesser of adjusted statutory net income or 10 of statutory policyholders' surplus as of the preceding calendar year end.
Percentage of statutory policyholders' surplus used to determine maximum allowable dividends (in hundredths)	10.00%

Disclosure of statutory restrictions on the payment of dividends as prescribed by the National Association of Insurance Commissioners or state regulatory authorities, amounts not available for future dividend payments, and amount of dividends paid.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 60

-Paragraph 60

-Subparagraph h

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 505

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6486098&loc=d3e24708-158529

Name:	us-gaap_StatutoryDividendPaymentRestrictionsDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration