Investments (Narrative) (Details) (USD $)	3 Months Ended					12 Months Ended		3 Months Ended		1 Months Ended	3 Months Ended		0 Months Ended	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014 Minimum [Member]	Mar. 31, 2014 Maximum [Member]	Apr. 30, 2014 Subsequent Event [Member]	Mar. 31, 2014 Corinthian Colleges, Inc. [Member]	Mar. 31, 2014 Classified Ventures LLC [Member]	Apr. 02, 2014 Classified Ventures' sale of apartments.com [Member] Subsequent Event [Member]	Jun. 30, 2014 Classified Ventures' sale of apartments.com [Member] Subsequent Event [Member] Scenario, Forecast [Member]
Schedule of Investments [Line Items]
New investments in marketable equity securities	$ 0				$ 0
Proceeds from sales of marketable equity securities	4,200,000				2,100,000
Proceeds from sales of marketable securities in Q1 settled in April										400,000
(Loss) gain on sales of marketable equity securities	(300,000)				600,000
Impairment write-down on a marketable equity security											500,000
Investments in commercial paper	99,900,000
Investment maturity length for commercial paper								3 months 1 day	6 months
Cash distribution from equity method investment													95,000,000
Pre-tax gain on equity method investments	4,052,000	37,000	5,892,000	3,868,000	3,418,000	13,215,000	14,086,000							92,000,000
Percentage owned of equity method investment												16.50%
Company's investments in marketable equity securities	510,697,000	487,156,000				487,156,000
Unrealized loss on investment	$ 317,961,000	$ 289,438,000				$ 289,438,000