Notes Receivable (Details) (USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Notes Receivable (Textuals) [Abstract]
Interest Income	$ 3.2	$ 3.2	$ 6.3	$ 6.4
Interest accrued on bonds	3.1	3.1	6.2	6.2
Amortization of the discount	0.1	0.1	0.1	0.1
Payment received relating to notes receivables			$ 10.7	$ 11.8

This item represents the amount of amortization of purchase discount related to an investment in debt securities. The purchase discount is amortized to income over the life (holding period) of the security to arrive at an amount of periodic interest income which results in a constant effective yield on the investment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 14

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 91
-Paragraph 18

Name:	us-gaap_InvestmentIncomeAmortizationOfDiscount
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration