Fair Value Measurements (Narrative) (Details) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Impairment recognized, related to long-lived assets	$ 1,100,000	$ 1,400,000
Short term investments	5,286,000	5,286,000	4,016,000
Estimated fair value of obligation contained in various acquisition agreements		4,500,000	3,300,000
Carrying value of held-to-maturity investments	1,600,000	1,600,000	1,500,000
Fair value of held-to-maturity investments	$ 1,800,000	$ 1,800,000	$ 1,700,000
Base Rate [Member]
Debt Instrument [Line Items]
Credit risk basis points		175.00
Eurodollar Rate [Member]
Debt Instrument [Line Items]
Credit risk basis points		275.00