Investments (Investments in Marketable Securities) (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities		$ 0
Available-for-sale - short-term:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 23,271,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(22,000)
Fair Value	23,249,000
Available-for-sale - short-term: | U.S. Treasury, government and agency debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,485,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(22,000)
Fair Value	10,463,000
Available-for-sale - short-term: | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,786,000
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	12,786,000
Available-for-sale - long-term: | U.S. Treasury, government and agency debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,529,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(46,000)
Fair Value	$ 13,483,000