Supplementary Balance Sheet Data (Details) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Supplementary Balance Sheet Data
Accounts receivable - allowance for doubtful accounts	$ 70.8	$ 78.5	$ 70.2
Accounts receivable - allowance for sales returns	145.5	197.3	138.0
Prepublication costs - accumulated amortization	955.3	1,089.3	948.4
Property and equipment - accumulated depreciation	$ 1,113.8	$ 1,064.8	$ 1,023.4