Fair Value Measurements (Narrative) (Details) (USD $)	6 Months Ended							6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jun. 30, 2012 Designated as Hedging Instrument [Member]	Dec. 31, 2011 Designated as Hedging Instrument [Member]	Jun. 30, 2012 Credit Agreement [Member]	Jul. 16, 2010 Credit Agreement [Member]	Jun. 30, 2012 Interest Rate Swap [Member]	Jun. 30, 2011 Interest Rate Swap [Member]	Jun. 30, 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]	Jun. 30, 2012 Interest Rate Swap [Member] Minimum [Member]	Jun. 30, 2012 Interest Rate Swap [Member] Maximum [Member]	Jul. 16, 2010 Interest Rate Swap [Member] Credit Agreement [Member]
Fair Value Disclosures [Line Items]
(Losses)/gains recognized in income, net	$ 100,000	$ 300,000
Amount of credit facility						390,000,000	390,000,000
Notional amount														105,000,000
Fixed interest rate in swap												2.00%	2.75%	2.04%
Liability Derivative	4,914,000		4,251,000	4,914,000	4,251,000					4,914,000	4,251,000
Interest expense								$ 800,000	$ 900,000