Investments and Fair Value Measurements - Cash, Cash Equivalents and Investments (Details) - USD ($)		3 Months Ended	9 Months Ended
		Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Cash, cash equivalents and investments [Abstract]
Cash		$ 16,957,000	$ 16,957,000		$ 10,289,000
Cash equivalents [Abstract]
Certificates of deposit	[1]	12,704,000	12,704,000		14,586,000
Total cash and cash equivalents		29,661,000	29,661,000	$ 26,185,000	24,875,000	$ 28,814,000
Amortized Cost		47,244,000	47,244,000		43,646,000
Gross Unrealized Gain		137,000	137,000		433,000
Gross Unrealized (Loss)		(33,000)	(33,000)		(76,000)
Fair Value		47,348,000	47,348,000		44,003,000
Contractual maturities on investments, amortized cost basis [Abstract]
Due within 1 year		9,436,000	9,436,000		11,022,000
Due after 1 through 5 years		8,147,000	8,147,000		7,749,000
Investments, amortized cost		17,583,000	17,583,000		18,771,000
Contractual maturities on investments, fair value basis [Abstract]
Due within 1 year		9,563,000	9,563,000		11,437,000
Due after 1 through 5 years		8,124,000	8,124,000		7,691,000
Investments, fair value		17,687,000	17,687,000		19,128,000
Investments held		7,025,000	7,025,000		7,948,000
Gross realized gains from sales of available-for-sale investments			429,000	859,000
GHI
Contractual maturities on investments, fair value basis [Abstract]
Proceeds from sales of available-for-sale investments			581,000
Realized gain		113,000
Available-for-sale investments, expenses		29,000	152,000
Gross realized gains from sales of available-for-sale investments		84,000	429,000
Unrealized gain, net of tax			135,000
IntelliEpi
Contractual maturities on investments, fair value basis [Abstract]
Proceeds from sales of available-for-sale investments				902,000
Available-for-sale investments, expenses				43,000
Gross realized gains from sales of available-for-sale investments				$ 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		17,583,000	17,583,000		18,771,000
Gross Unrealized Gain		137,000	137,000		433,000
Gross Unrealized (Loss)		(33,000)	(33,000)		(76,000)
Fair Value		17,687,000	17,687,000		19,128,000
Certificates of Deposit [Member]
Cash equivalents [Abstract]
Amortized Cost	[2]	9,047,000	9,047,000		9,795,000
Gross Unrealized Gain	[2]	2,000	2,000		1,000
Gross Unrealized (Loss)	[2]	(9,000)	(9,000)		(13,000)
Fair Value	[2]	9,040,000	9,040,000		9,783,000
Corporate Bonds [Member]
Cash equivalents [Abstract]
Amortized Cost		8,488,000	8,488,000		8,776,000
Gross Unrealized (Loss)		(24,000)	(24,000)		(63,000)
Fair Value		8,464,000	8,464,000		8,713,000
Corporate Equity Securities [Member]
Cash equivalents [Abstract]
Amortized Cost		48,000	48,000		200,000
Gross Unrealized Gain		135,000	135,000		432,000
Fair Value		$ 183,000	$ 183,000		$ 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.