Investments (Narrative) (Details) - USD ($)		3 Months Ended							9 Months Ended		12 Months Ended
	Jun. 30, 2014	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Apr. 01, 2014
Schedule of Investments [Line Items]
Commercial paper and money market investments		$ 804,700,000			$ 594,300,000				$ 804,700,000		$ 594,300,000
New investments in marketable equity securities									135,600,000	$ 0
Proceeds from sales of marketable equity securities									0	5,800,000
(Loss) gain on sales of marketable equity securities										(2,600,000)
Gain on Berkshire marketable equity securities exchange		0				$ 0			0	266,733,000
Pre-tax gain on equity method investments		$ 95,000	$ (353,000)	$ (404,000)	$ 202,000	$ 4,613,000	$ 91,503,000	$ 4,052,000	$ (662,000)	$ 100,168,000	$ 100,370,000	$ 13,215,000
Corinthian Colleges, Inc. [Member]
Schedule of Investments [Line Items]
Impairment write-down on a marketable equity security								$ 500,000
Berkshire Exchange Transaction [Member] | Berkshire Hathaway Inc [Member]
Schedule of Investments [Line Items]
Gain on Berkshire marketable equity securities exchange	$ 266,700,000
Berkshire Exchange Transaction [Member] | Berkshire Hathaway Inc [Member] | Common Class A [Member]
Schedule of Investments [Line Items]
Number of Shares Exchanged	2,107						2,107
Berkshire Exchange Transaction [Member] | Berkshire Hathaway Inc [Member] | Common Class B [Member]
Schedule of Investments [Line Items]
Number of Shares Exchanged	1,278						1,278
HomeHero [Member]
Schedule of Investments [Line Items]
Percentage of interest acquired			20.00%
Residential Home Health Illinois [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage		40.00%							40.00%
Residential Hospice Illinois [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage		42.50%							42.50%
Celtic Healthcare Allegheny Health Network Joint Venture [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage		40.00%							40.00%
Classified Ventures' sale of apartments.com [Member]
Schedule of Investments [Line Items]
Cash distribution from equity method investment													$ 95,000,000
Pre-tax gain on equity method investments							$ 90,900,000