Pledged Treasury Securities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2007
Pledged Treasury Securities [Abstract]
Mortgage debt defeased in connection to sale		$ 29.3
Defeasance trust and deposit of proceeds		31.1
Approximate market value	$ 23.3

Value of the investment at close of period. For schedules of investments that are categorized, the value would be aggregated by category. For investment in and advances to affiliates, if operations of any controlled companies are different in character from those of the company, group such affiliates within divisions and by type of activities.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 12

-Paragraph 3, 4

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 14

-Paragraph 2, 3

-Article 12

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 320

-Section S99

-Paragraph 5

-Subparagraph (SX 210.12-13.Column C.6)

-URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611282-123010

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 13

-Paragraph Column C

-Article 12

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 320

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-12.Column C.3,4)

-URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611133-123010

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 13

-Paragraph 6

-Article 12

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 320

-Section S99

-Paragraph 6

-Subparagraph (SX 210.12-14.Column E.2,3)

-URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611322-123010

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 12

-Paragraph Column C

-Article 12

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 14

-Paragraph Column E

-Article 12

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 12C

-Paragraph 7

-Article 12

Reference 11: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 320

-Section S99

-Paragraph 4

-Subparagraph (SX 210.12-12C.Column C.7)

-URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611225-123010

Reference 12: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 12C

-Paragraph Column C

-Article 12

+ Details