Other Financial Information (Schedule of Marketable Securities) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Marketable Securities [Abstract]
Amortized Cost	$ 45,728,000		$ 45,728,000		$ 51,989,000
Gross Unrealized Gains	239,000		239,000		172,000
Gross Unrealized Losses	(6,000)		(6,000)		(21,000)
Estimated Fair Value	45,961,000		45,961,000		52,140,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Marketable Securities, Realized Loss, Other than Temporary Impairments, Amount	0	0	0	0
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments	0	0	0	0
U.S. treasury securities
Marketable Securities [Abstract]
Amortized Cost	35,002,000		35,002,000		40,019,000
Gross Unrealized Gains	3,000		3,000		8,000
Gross Unrealized Losses	0		0		(12,000)
Estimated Fair Value	35,005,000		35,005,000		40,015,000
Certificates of deposit
Marketable Securities [Abstract]
Amortized Cost	10,496,000		10,496,000		11,746,000
Gross Unrealized Gains	0		0		1,000
Gross Unrealized Losses	(6,000)		(6,000)		(9,000)
Estimated Fair Value	10,490,000		10,490,000		11,738,000
Mutual Funds
Marketable Securities [Abstract]
Amortized Cost	230,000		230,000		224,000
Gross Unrealized Gains	236,000		236,000		163,000
Gross Unrealized Losses	0		0		0
Estimated Fair Value	$ 466,000		$ 466,000		$ 387,000