Fair Value Measurements (Marketable Debt Securities) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Amortized Cost, Total	$ 30,912,000	$ 42,947,000	$ 50,997,000
Gross Unrealized Gains, Total	434,000	568,000	1,651,000
Gross Unrealized Losses, Total	(9,000)	(78,000)
Marketable securities, at fair value	31,337,000	43,437,000	52,648,000
Other-than-temporary Impairments, Investments
Other Than Available For Sale Municipal Bonds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Amortized Cost, Total	2,167,000	18,029,000	50,997,000
Gross Unrealized Gains, Total	82,000	568,000	1,651,000
Marketable securities, at fair value	2,249,000	18,597,000	52,648,000
Other-than-temporary Impairments, Investments
Municipal Bonds - Available For Sale [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Amortized Cost, Total	28,745,000	24,918,000
Gross Unrealized Gains, Total	352,000
Gross Unrealized Losses, Total	(9,000)	(78,000)
Marketable securities, at fair value	29,088,000	24,840,000
Other-than-temporary Impairments, Investments