Variable Interest Entities (Details) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Variable Interest Entities (Textuals) [Abstract]
Total assets in joint ventures	$ 101.0	$ 95.3
Total liabilities in joint ventures	$ 89.9	$ 78.4

Quantifies the net carrying amount of the entity's liabilities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS140-4 and FIN46(R)-8
-Paragraph C6
-Subparagraph c

Name:	us-gaap_VariableInterestCarryingAmountLiabilities
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant