Summary of Quarterly Operating Results and Comprehensive Income (Unaudited) (Quarterly Impact of Certain Items) (Details 2) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Quarterly Impact of Certain Items [Line Items]
Write-down of marketable equity securities, after tax					$ 6.7					$ 6.7
Write-down on marketable equity securities, per share (dollars per share)					$ (0.91)
Non-operating unrealized foreign currency gains (losses), after tax	(5.5)	(6.8)	1.9	3.2	(2.6)	5.0	(8.1)	(3.0)	(7.1)	(8.6)
Non-operating unrealized foreign currency gains (losses), per share (dollars per share)	$ (0.94)	$ (1.16)	$ 0.25	$ 0.44	$ (0.35)	$ 0.69	$ (1.11)	$ (0.41)
Classified Ventures LLC [Member]
Quarterly Impact of Certain Items [Line Items]
Gain on sale of equity method investment, net of tax	249.8								249.8
Gain on sale of equity method investment, per share (dollars per share)	$ 42.89
Classified Ventures' sale of apartments.com [Member]
Quarterly Impact of Certain Items [Line Items]
Gain from equity method investments, net of tax			58.2						58.2
Gain from equity method investments, per share (dollars per share)			$ 7.80
Education [Member]
Quarterly Impact of Certain Items [Line Items]
Severance and restructuring costs, after tax					12.2	3.1	3.9	6.1		25.3
Severance and restructuring costs, per share (dollars per share)					$ (1.66)	$ (0.42)	$ (0.54)	$ (0.85)
Impairment of intangible and other long-lived assets, after tax					3.2					3.2
Impairment of intangible and other long-lived assets, per share (dollars per share)					$ (0.44)
Education division and corporate office [Member]
Quarterly Impact of Certain Items [Line Items]
Early retirement program expense and related charges, restructuring charges and software asset write-offs, after tax	1.9	8.7	6.7	2.9					20.2
Early retirement program expense and related charges, restructuring charges and software asset write-offs, per share (dollars per share)	$ (0.33)	$ (1.50)	$ (0.90)	$ (0.39)
Kaplan and other businesses [Member]
Quarterly Impact of Certain Items [Line Items]
Impairment of intangible and other long-lived assets, after tax	11.2								11.2
Impairment of intangible and other long-lived assets, per share (dollars per share)	$ (1.92)
Corporate Office [Member]
Quarterly Impact of Certain Items [Line Items]
Gain on sale of Corporate headquarters building, net of tax				81.8					81.8
Gain on sale of Corporate headquarters building, per share (dollars per share)				$ 11.13
Cable [Member] | Wireless Licenses [Member]
Quarterly Impact of Certain Items [Line Items]
Gain on sale of intangible assets, net of tax		48.2							48.2
Gain on sale of intangible assets, per share (dollars per share)		$ 8.29
Berkshire Exchange Transaction [Member]
Quarterly Impact of Certain Items [Line Items]
Gain on Berkshire Exchange, net of tax			$ 266.7						$ 266.7
Gain on Berkshire Exchange, per share (dollars per share)			$ 35.73