Financial Instruments and Marketable Securities - Marketable Securities Treated as Available-for-Sale Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities, Amortized Cost	$ 197	$ 197	$ 197
Total available-for-sale securities, Gross Unrealized Gains	256	254	220
Total available-for-sale securities, Gross Unrealized Losses	0	0	0
Total available-for-sale securities, Fair Value	453	451	417
Common stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities, Amortized Cost	197	197	197
Total available-for-sale securities, Gross Unrealized Gains	256	254	220
Total available-for-sale securities, Gross Unrealized Losses	0	0	0
Total available-for-sale securities, Fair Value	$ 453	$ 451	$ 417