Fair Value Measurements (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 months	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Number of months investment-related assets have been in a continuous loss position	12
Recorded net gains (losses) on investments	$ 43,000	$ (249,000)	$ 396,000
Gain (loss) on investment of marketable securities		$ (200,000)	$ 400,000