Fair Value Measurements (Narrative) (Details) (USD $)	12 Months Ended						12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jul. 16, 2010 Credit Agreement [Member]	Dec. 31, 2011 Interest Rate Swap [Member] Designated as Hedging Instrument [Member] Other Noncurrent Liabilities [Member]	Dec. 31, 2010 Interest Rate Swap [Member] Designated as Hedging Instrument [Member] Other Noncurrent Liabilities [Member]	Dec. 31, 2011 Interest Rate Swap [Member] Credit Agreement [Member]	Dec. 31, 2010 Interest Rate Swap [Member] Credit Agreement [Member]	Jul. 16, 2010 Interest Rate Swap [Member] Credit Agreement [Member]	Dec. 31, 2011 Interest Rate Swap [Member] Credit Agreement [Member] Minimum [Member]	Dec. 31, 2011 Interest Rate Swap [Member] Credit Agreement [Member] Maximum [Member]
Fair Value Disclosures [Line Items]
(Losses)/gains recognized in income, net	$ (600,000)	$ (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 Derivatives	4,251,000	452,000			4,251,000	452,000
Interest expense	$ 20,148,000	$ 18,405,000	$ 21,368,000				$ 1,900,000	$ 800,000