Fair Value Measurements (Narrative) (Details) (USD $)	3 Months Ended						3 Months Ended
	Mar. 31, 2011	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Designated as Hedging Instrument [Member]	Dec. 31, 2011 Designated as Hedging Instrument [Member]	Jul. 16, 2010 Credit Agreement [Member]	Mar. 31, 2012 Interest Rate Swap [Member]	Mar. 31, 2011 Interest Rate Swap [Member]	Mar. 31, 2012 Interest Rate Swap [Member] Designated as Hedging Instrument [Member] Other Noncurrent Liabilities [Member]	Dec. 31, 2011 Interest Rate Swap [Member] Designated as Hedging Instrument [Member] Other Noncurrent Liabilities [Member]	Jul. 16, 2010 Interest Rate Swap [Member] Credit Agreement [Member]	Mar. 31, 2012 Interest Rate Swap [Member] Credit Agreement [Member] Minimum [Member]	Mar. 31, 2012 Interest Rate Swap [Member] Credit Agreement [Member] Maximum [Member]
Fair Value Disclosures [Line Items]
(Losses)/gains recognized in income, net	$ 200,000
Amount of credit facility						390,000,000
Notional amount											105,000,000
Fixed interest rate in swap											2.04%
Credit spread												2.00%	2.75%
Liability Derivative		4,597,000	4,251,000	4,597,000	4,251,000				4,597,000	4,251,000
Interest expense							$ 400,000	$ 500,000