Marketable Securities - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Fixed Income Securities	$ 3,000,000		$ 5,300,000
Purchases of marketable securities	0	$ 18,876,000
Proceeds from sales of marketable securities	2,344,000	10,185,000
Realized gains on sale of marketable securities	3,000	192,000
Unrealized holding gain arising during the period	$ 3,000	$ 7,000
Marketable securities, effective maturity period (in years)	11 months 27 days
Marketable securities, average effective duration (in years)	1 month 21 days