Fair Value of Financial Instruments - Carrying Value (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Assets:
Marketable securities	$ 28,038,000	$ 37,940,000
Long term marketable securities	55,009,000	19,816,000
Liabilities:
Derivative liabilities	854,000	6,564,000
Quoted Prices in Active Markets (Level 1) | Recurring
Assets:
Cash and cash equivalents	34,152,000	36,396,000
Total assets at fair value	34,152,000	36,396,000
Significant Other Observable Inputs (Level 2) | Recurring
Assets:
Marketable securities	28,038,000	37,940,000
Long term marketable securities	55,009,000	19,816,000
Marketable securities - restricted (SERP)	263,000	305,000
Total assets at fair value	83,310,000	58,061,000
Significant Unobservable Inputs (Level 3) | Recurring
Liabilities:
Derivative liabilities	854,000	6,564,000
Warrants outstanding	0
Total Carrying Value | Recurring
Assets:
Cash and cash equivalents	34,152,000	36,396,000
Marketable securities	28,038,000	37,940,000
Long term marketable securities	55,009,000	19,816,000
Marketable securities - restricted (SERP)	263,000	305,000
Total assets at fair value	117,462,000	94,457,000
Liabilities:
Derivative liabilities	$ 854,000	$ 6,564,000