Fair Value Measurements Variable Interest Entity (Details) (USD $) In Millions	6 Months Ended
	Jun. 30, 2011	Dec. 31, 2004
Variable Interest Entity [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Date Involvement Began	2004
Variable Interest Entity Amount Of Installment Note And Letter Of Credit Contributed To Special Purpose Entity		$ 25.0
Variable Interest Entity Amount Of Cash Received		22.6
Variable Interest Entity Interest Cash Payments Received Net	immaterial cash payments
Variable Interest Entity Recorded Liability For Performance Obligation	de minimus guarantee liability
Variable Interest Entity Cash Received Upon Maturity	2.6
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Amount Of Notes Issued By Special Purpose Entity		22.6
Variable Interest Entity Term Of Notes Issued By Special Purpose Entity		15-year
Variable Interest Entity Investment	$ 2.6
Variable Interest Entity Maturity Date Of Notes Issued By Special Purpose Entity	2019