Investments and Fair Value Measurements (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012		Dec. 31, 2011
Cash, cash equivalents and investments [Abstract]
Cash	$ 25,789,000		$ 26,250,000
Cash Equivalents, at Carrying Value [Abstract]
Money market funds	3,000		4,384,000
Cash Equivalents, at Carrying Value, Total	3,000		4,384,000
Cash and Cash Equivalents, at Carrying Value, Total	25,792,000	31,156,000	30,634,000	[1]	26,156,000
Amortized Cost	49,436,000		50,144,000
Gross Unrealized Gain	12,000		16,000
Gross Unrealized (Loss)	(78,000)		(65,000)
Fair Value	49,370,000		50,095,000
Contractual maturities on investments, amortized cost basis [Abstract]
Due within 1 year	6,536,000		10,288,000
Due after 1 through 5 years	17,108,000		9,222,000
Investments, amortized cost	23,644,000		19,510,000
Contractual maturities on investments, fair value basis [Abstract]
Due within 1 year	6,540,000		10,270,000
Due after 1 through 5 years	17,038,000		9,191,000
Investments, fair value	23,578,000		19,461,000
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities	8,100,000	2,700,000
Summary of fair value and gross unrealized losses related to available-for-sale securities [Abstract]
Fair value, in loss position less than twelve months	15,741,000		8,323,000
Gross unrealized loss, in loss position less than twelve months	(78,000)		(41,000)
Fair value, in loss position greater than twelve months	0		1,701,000
Gross unrealized loss, in loss position greater than twelve months	0		(24,000)
Fair value, total in loss position	15,741,000		10,024,000
Gross unrealized loss, total in loss position	(78,000)		(65,000)
Investment in privately held Companies [Abstract]
Minority investments in unconsolidated privately-held companies	392,000		392,000
Assets [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	25,792,000		30,634,000
Recurring [Member]
Assets [Abstract]
Assets, fair value	23,581,000		23,845,000
Liabilities [Abstract]
Liabilities, fair value	0		0
Recurring [Member] | Quoted Prices in Active Markets of Identical Assets (Level 1) [Member]
Assets [Abstract]
Assets, fair value	3,000		4,384,000
Liabilities [Abstract]
Liabilities, fair value	0		0
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets [Abstract]
Assets, fair value	23,578,000		19,461,000
Liabilities [Abstract]
Liabilities, fair value	0		0
Recurring [Member] | Money market fund - cash [Member]
Assets [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	3,000		4,384,000
Recurring [Member] | Money market fund - cash [Member] | Quoted Prices in Active Markets of Identical Assets (Level 1) [Member]
Assets [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	3,000		4,384,000
Recurring [Member] | Money market fund - cash [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0		0
Recurring [Member] | Certificates of deposit [Member]
Assets [Abstract]
Available-for-sale Securities, Fair Value Disclosure	6,999,000		6,645,000
Recurring [Member] | Certificates of deposit [Member] | Quoted Prices in Active Markets of Identical Assets (Level 1) [Member]
Assets [Abstract]
Available-for-sale Securities, Fair Value Disclosure	0		0
Recurring [Member] | Certificates of deposit [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets [Abstract]
Available-for-sale Securities, Fair Value Disclosure	6,999,000		6,645,000
Recurring [Member] | Corporate bonds [Member]
Assets [Abstract]
Available-for-sale Securities, Fair Value Disclosure	16,579,000		12,816,000
Recurring [Member] | Corporate bonds [Member] | Quoted Prices in Active Markets of Identical Assets (Level 1) [Member]
Assets [Abstract]
Available-for-sale Securities, Fair Value Disclosure	0		0
Recurring [Member] | Corporate bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets [Abstract]
Available-for-sale Securities, Fair Value Disclosure	16,579,000		12,816,000
Other assets [Member]
Investment in privately held Companies [Abstract]
Investments in privately-held companies	9,500,000		9,400,000
Minority investments in unconsolidated privately-held companies	392,000		392,000
Certificates of deposit [Member]
Cash Equivalents, at Carrying Value [Abstract]
Amortized Cost	6,998,000		6,638,000
Gross Unrealized Gain	8,000		9,000
Gross Unrealized (Loss)	(7,000)		(2,000)
Fair Value	6,999,000		6,645,000
Summary of fair value and gross unrealized losses related to available-for-sale securities [Abstract]
Fair value, in loss position less than twelve months	2,953,000		1,877,000
Gross unrealized loss, in loss position less than twelve months	(7,000)		(1,000)
Fair value, in loss position greater than twelve months	0		199,000
Gross unrealized loss, in loss position greater than twelve months	0		(1,000)
Fair value, total in loss position	2,953,000		2,076,000
Gross unrealized loss, total in loss position	(7,000)		(2,000)
Corporate bonds [Member]
Cash Equivalents, at Carrying Value [Abstract]
Amortized Cost	16,646,000		12,872,000
Gross Unrealized Gain	4,000		7,000
Gross Unrealized (Loss)	(71,000)		(63,000)
Fair Value	16,579,000		12,816,000
Summary of fair value and gross unrealized losses related to available-for-sale securities [Abstract]
Fair value, in loss position less than twelve months	12,788,000		6,446,000
Gross unrealized loss, in loss position less than twelve months	(71,000)		(40,000)
Fair value, in loss position greater than twelve months	0		1,502,000
Gross unrealized loss, in loss position greater than twelve months	0		(23,000)
Fair value, total in loss position	12,788,000		7,948,000
Gross unrealized loss, total in loss position	(71,000)		(63,000)
Total Investments [Member]
Cash Equivalents, at Carrying Value [Abstract]
Amortized Cost	23,644,000		19,510,000
Gross Unrealized Gain	12,000		16,000
Gross Unrealized (Loss)	(78,000)		(65,000)
Fair Value	$ 23,578,000		$ 19,461,000

[1] The condensed consolidated balance sheet at December 31, 2012 has been derived from the audited consolidated financial statements at that date.