Fair Value Measurements (Marketable Debt Securities) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Amortized Cost, Total	$ 21,111	$ 30,912	$ 42,947
Gross Unrealized Gains, Total	220	434	568
Gross Unrealized Losses, Total	(9)	(9)	(78)
Marketable securities, at fair value	21,322	31,337	43,437
Other-than-temporary Impairments, Investments	0	0	0
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	18,029
Gross Unrealized Gains, Total		82	568
Gross Unrealized Losses, Total		0	0
Marketable securities, at fair value		2,249	18,597
Other-than-temporary Impairments, Investments		0	0
Municipal Bonds - Available For Sale [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Amortized Cost, Total	21,111	28,745	24,918
Gross Unrealized Gains, Total	220	352	0
Gross Unrealized Losses, Total	(9)	(9)	(78)
Marketable securities, at fair value	21,322	29,088	24,840
Other-than-temporary Impairments, Investments	$ 0	$ 0	$ 0