Marketable Securities (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Gain (Loss) on Investments [Line Items]
Maximum maturity of debt securities, years	3 years
Net pre-tax unrealized gains (losses) for marketable securities	$ 40,000		$ (17,000)
Maximum time for loss position, months	12 months		12 months
Proceeds from sale of marketable securities	2,453,000	1,350,000
Recognized loss from the sale of marketable securities	(23,000)
Marketable securities classified as cash equivalents, Recorded basis	1,055,000		2,824,000
Foreign Accounts [Member]
Gain (Loss) on Investments [Line Items]
Cash and marketable securities held in foreign accounts	3,113,000		3,585,000
Debt Securities Unrealized Gain Position [Member]
Gain (Loss) on Investments [Line Items]
Fair value	19,460,000		19,012,000
Unrealized gain	41,000		42,000
Debt Securities Unrealized Loss Position [Member]
Gain (Loss) on Investments [Line Items]
Fair value	2,467,000		2,819,000
Unrealized loss	$ (4,000)		$ (59,000)