Investments and Fair Value Measurements - Investment Category and Length (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Summary of fair value and gross unrealized losses related to available-for-sale securities [Abstract]
Fair value, in loss position less than twelve months	$ 7,024,000	$ 11,375,000
Gross unrealized loss, in loss position less than twelve months	(21,000)	(67,000)
Fair value, in loss position greater than twelve months	2,794,000	5,390,000
Gross unrealized loss, in loss position greater than twelve months	(2,000)	(9,000)
Fair value, total in loss position	9,818,000	16,765,000
Gross unrealized loss, total in loss position	(23,000)	(76,000)
Minority Investments [Abstract]
Minority investments in unconsolidated privately-held companies	3
Certificates of Deposit [Member]
Summary of fair value and gross unrealized losses related to available-for-sale securities [Abstract]
Fair value, in loss position less than twelve months	1,919,000	4,509,000
Gross unrealized loss, in loss position less than twelve months		(11,000)
Fair value, in loss position greater than twelve months	960,000	3,543,000
Gross unrealized loss, in loss position greater than twelve months	(1,000)	(2,000)
Fair value, total in loss position	2,879,000	8,052,000
Gross unrealized loss, total in loss position	(1,000)	(13,000)
Corporate Bonds [Member]
Summary of fair value and gross unrealized losses related to available-for-sale securities [Abstract]
Fair value, in loss position less than twelve months	5,105,000	6,866,000
Gross unrealized loss, in loss position less than twelve months	(21,000)	(56,000)
Fair value, in loss position greater than twelve months	1,834,000	1,847,000
Gross unrealized loss, in loss position greater than twelve months	(1,000)	(7,000)
Fair value, total in loss position	6,939,000	8,713,000
Gross unrealized loss, total in loss position	(22,000)	(63,000)
Other Assets [Member]
Minority Investments [Abstract]
Investments in privately-held companies	$ 11,700,000	$ 12,100,000