Investments and Fair Value Measurements - Cash, Cash Equivalents and Investments (Details) - USD ($)		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Cash, cash equivalents and investments [Abstract]
Cash		$ 15,810,000		$ 10,289,000
Cash equivalents [Abstract]
Certificates of deposit	[1]	9,257,000		14,586,000
Total cash and cash equivalents		25,067,000	$ 33,285,000	24,875,000	$ 28,814,000
Amortized Cost		42,949,000		43,646,000
Gross Unrealized Gain		405,000		433,000
Gross Unrealized (Loss)		(23,000)		(76,000)
Fair Value		43,331,000		44,003,000
Contractual maturities on investments, amortized cost basis [Abstract]
Due within 1 year		8,654,000		11,022,000
Due after 1 through 5 years		9,228,000		7,749,000
Investments, amortized cost		17,882,000		18,771,000
Contractual maturities on investments, fair value basis [Abstract]
Due within 1 year		9,053,000		11,437,000
Due after 1 through 5 years		9,211,000		7,691,000
Investments, fair value		18,264,000		19,128,000
Gross realized gains from sales of available-for-sale investments		181,000	367,000
GHI
Contractual maturities on investments, fair value basis [Abstract]
Realized gain		246,000
Available-for-sale investments, expenses		65,000
Gross realized gains from sales of available-for-sale investments		181,000
Unrealized gain, net of tax		398,000
IntelliEpi
Contractual maturities on investments, fair value basis [Abstract]
Investments held		0
Realized gain			387,000
Available-for-sale investments, expenses			20,000
Gross realized gains from sales of available-for-sale investments			$ 367,000
Auction Rate Securities [Member]
Contractual maturities on investments, fair value basis [Abstract]
Investments, fair value		0
Total Investments [Member]
Cash equivalents [Abstract]
Amortized Cost		17,882,000		18,771,000
Gross Unrealized Gain		405,000		433,000
Gross Unrealized (Loss)		(23,000)		(76,000)
Fair Value		18,264,000		19,128,000
Certificates of Deposit [Member]
Cash equivalents [Abstract]
Amortized Cost	[2]	9,084,000		9,795,000
Gross Unrealized Gain	[2]	5,000		1,000
Gross Unrealized (Loss)	[2]	(1,000)		(13,000)
Fair Value	[2]	9,088,000		9,783,000
Corporate Bonds [Member]
Cash equivalents [Abstract]
Amortized Cost		8,663,000		8,776,000
Gross Unrealized Gain		2,000
Gross Unrealized (Loss)		(22,000)		(63,000)
Fair Value		8,643,000		8,713,000
Corporate Equity Securities [Member]
Cash equivalents [Abstract]
Amortized Cost		135,000		200,000
Gross Unrealized Gain		398,000		432,000
Fair Value		$ 533,000		$ 632,000

[1] Certificate of deposit with original maturities of less than 90 days.

[2] Certificate of deposit with original maturities of more than 90 days.