Investments and Fair Value Measurements - Cash, Cash Equivalents and Investments (Details) - USD ($)		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Cash, cash equivalents and investments [Abstract]
Cash		$ 13,364,000		$ 13,364,000		$ 10,289,000
Cash equivalents [Abstract]
Certificates of deposit	[1]	12,751,000		12,751,000		14,586,000
Total cash and cash equivalents		26,115,000	$ 28,640,000	26,115,000	$ 28,640,000	24,875,000	$ 28,814,000
Amortized Cost		44,746,000		44,746,000		43,646,000
Gross Unrealized Gain		235,000		235,000		433,000
Gross Unrealized (Loss)		(19,000)		(19,000)		(76,000)
Fair Value		44,962,000		44,962,000		44,003,000
Contractual maturities on investments, amortized cost basis [Abstract]
Due within 1 year		10,249,000		10,249,000		11,022,000
Due after 1 through 5 years		8,382,000		8,382,000		7,749,000
Investments, amortized cost		18,631,000		18,631,000		18,771,000
Contractual maturities on investments, fair value basis [Abstract]
Due within 1 year		10,460,000		10,460,000		11,437,000
Due after 1 through 5 years		8,387,000		8,387,000		7,691,000
Investments, fair value		18,847,000		18,847,000		19,128,000
Gross realized gains from sales of available-for-sale investments				345,000	859,000
GHI
Contractual maturities on investments, fair value basis [Abstract]
Proceeds from sales of available-for-sale investments				468,000
Realized gain		222,000
Available-for-sale investments, expenses		58,000		123,000
Gross realized gains from sales of available-for-sale investments		164,000		345,000
Unrealized gain, net of tax				223,000
IntelliEpi
Contractual maturities on investments, fair value basis [Abstract]
Proceeds from sales of available-for-sale investments			515,000		902,000
Available-for-sale investments, expenses			23,000		43,000
Gross realized gains from sales of available-for-sale investments			$ 492,000		$ 859,000
Auction Rate Securities [Member]
Contractual maturities on investments, fair value basis [Abstract]
Investments, fair value		0		0
Total Investments [Member]
Cash equivalents [Abstract]
Amortized Cost		18,631,000		18,631,000		18,771,000
Gross Unrealized Gain		235,000		235,000		433,000
Gross Unrealized (Loss)		(19,000)		(19,000)		(76,000)
Fair Value		18,847,000		18,847,000		19,128,000
Certificates of Deposit [Member]
Cash equivalents [Abstract]
Amortized Cost	[2]	9,957,000		9,957,000		9,795,000
Gross Unrealized Gain	[2]	3,000		3,000		1,000
Gross Unrealized (Loss)	[2]	(6,000)		(6,000)		(13,000)
Fair Value	[2]	9,954,000		9,954,000		9,783,000
Corporate Bonds [Member]
Cash equivalents [Abstract]
Amortized Cost		8,597,000		8,597,000		8,776,000
Gross Unrealized Gain		9,000		9,000
Gross Unrealized (Loss)		(13,000)		(13,000)		(63,000)
Fair Value		8,593,000		8,593,000		8,713,000
Corporate Equity Securities [Member]
Cash equivalents [Abstract]
Amortized Cost		77,000		77,000		200,000
Gross Unrealized Gain		223,000		223,000		432,000
Fair Value		$ 300,000		$ 300,000		$ 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.