Derivative Instruments And Hedging Activity (Narrative) (Details) (Commodity Contracts - Fuel [Member])	3 Months Ended
Mar. 31, 2012 gal
Commodity Contracts - Fuel [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of hedge (in gallons of fuel)	7,200,000
Derivative maturities, maximum	January 2013

Aggregate notional amount of price risk derivatives designated as a cash flow hedge with notional amounts expressed in nonmonetary units. For example the number of barrels specified in a fuel oil forward purchase contract.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624163-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Notional Amount

-URI http://asc.fasb.org/extlink&oid=6519104

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5579245-113959

Name:	us-gaap_NonmonetaryNotionalAmountOfPriceRiskCashFlowHedgeDerivatives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant