Investments - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales of marketable securities	$ 500,000	$ 34,000	$ 1,000,000	$ 141,000
Gross realized gains or losses from sales of marketable securities	$ 0	$ 0	$ 0	$ 0