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, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Quarterly Impact of Certain Items [Line Items]
Write-down of marketable equity securities, after tax	$ 6.7				$ 11.2				$ 6.7	$ 11.2
Write-down on marketable equity securities, per share (dollars per share)	$ 0.91				$ 1.54
Non-operating unrealized foreign currency gains (losses), after tax	(2.6)	5.0	(8.1)	(3.0)		1.9	(1.6)	1.7	(8.6)	2.0
Non-operating unrealized foreign currency gains (losses), per share (dollars per share)	$ (0.35)	$ 0.69	$ (1.11)	$ (0.41)		$ 0.26	$ (0.21)	$ 0.22
Gain on sale of cost method investment, after tax								3.7		3.7
Gain on sale of cost method investment, per share (dollars per share)								$ 0.48
Education [Member]
Quarterly Impact of Certain Items [Line Items]
Severance and restructuring costs, after tax	12.2	3.1	3.9	6.1	27.1	2.7	3.1		25.3	32.9
Severance and restructuring costs, per share (dollars per share)	$ 1.66	$ 0.42	$ 0.54	$ 0.85	$ 3.75	$ 0.37	$ 0.41
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
Test Preparation [Member]
Quarterly Impact of Certain Items [Line Items]
Goodwill and other long-lived assets impairment, after tax					$ 81.9					$ 81.9
Goodwill and other long-lived assets impairment, per share (dollars per share)					$ 11.33