Investments - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales of marketable securities	$ 7,716,000	$ 0	$ 8,716,000	$ 141,000
Gross realized gains or losses from sales of marketable securities	6,000	0	6,000	0
Gross proceeds associated with realized gains	7,204,000		7,204,000
Gross unrealized gains	31,000		31,000		$ 1,000
Unrealized gains reclassified out of accumulated other comprehensive income	$ 16,000	$ 0	$ 16,000	$ 0