Fair Value Measurements (Marketable Debt Securities) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Amortized Cost	$ 21,953	$ 21,111
Gross Unrealized Gains	130	220
Gross Unrealized Losses	(57)	(9)
Estimated Fair Value	22,026	21,322
Other-than-temporary Impairments	0	0
Municipal bonds - available for sale [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Amortized Cost	21,953	21,111
Gross Unrealized Gains	130	220
Gross Unrealized Losses	(57)	(9)
Estimated Fair Value	22,026	21,322
Other-than-temporary Impairments	$ 0	$ 0