Other Long-Term Liabilities- NJ Tax (Details) - USD ($) $ in Thousands	1 Months Ended				3 Months Ended		9 Months Ended
	Nov. 30, 2015	Dec. 31, 2014	Jan. 31, 2014	Jan. 31, 2013	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Investment and Other Income, Net					$ 398	$ 395	$ 1,611	$ 1,841
New Jersey Tax Benefit
Amount of tax benefit	$ 9,800	$ 1,900	$ 1,100	$ 800
Proceeds from sale of tax credits	$ 9,200	$ 1,800	$ 1,000	$ 800
Base of operations requirement (in years)							5 years
Investment and Other Income, Net					$ 0	$ 0	$ 500	$ 600