Consolidated Balance Sheet (Unaudited) (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Allowances for trade accounts receivable	$ 62,515	$ 60,236
Preferred Stock, par value	$ 0.01	$ 0.01
Preferred Stock, shares authorized	25,000	25,000
Preferred Stock, shares issued
Preferred Stock, shares outstanding
Treasury stock, shares	35,350	35,643
Common Class A [Member]
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	500,000	500,000
Common Stock, shares issued	187,386	185,127
Common Stock, shares outstanding	152,036	149,484
Common Class B [Member]
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	135,000	135,000
Common Stock, shares issued
Common Stock, shares outstanding