Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Accounts receivable, trade, allowance for doubtful accounts	$ 8,697	$ 8,321
Property and equipment, accumulated depreciation	166,959	156,885
Amortizable intangible assets, accumulated amortization	714,592	675,038
Deferred financing costs, accumulated amortization	$ 13	$ 16,388
Class A [Member]
Common stock, par value	$ 0.01	$ 0
Common stock, shares authorized	360,000,000	0
Common stock, shares issued	57,813,267	0
Common stock, shares outstanding	57,813,267	0
Class B [Member]
Common stock, par value	$ 0.01	$ 0
Common stock, shares authorized	90,000,000	0
Common stock, shares issued	13,534,408	0
Common stock, shares outstanding	13,534,408	0