Cash Equivalents, and Investments - Textuals (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013 Investment	Jun. 30, 2012	Jun. 30, 2013 Investment	Jun. 30, 2012	Dec. 31, 2012 Investment
Cash Equivalents and Investments [Abstract]
Privately-held investments, Other than temporary impairment	$ 400,000	$ 0	$ 400,000	$ 14,000,000
Privately-held investments	$ 46,300,000		$ 46,300,000		$ 32,000,000
Total investments in unrealized loss position	249		249		98