Consolidated Balance Sheet (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Allowance for doubtful accounts receivable, current	$ 5,891	$ 5,683
Redeemable preferred stock, par value	$ 0.1	$ 0.1
Redeemable preferred stock, shares authorized	20,000,000	20,000,000
Redeemable preferred stock, shares issued	6,111,000	6,361,000
Redeemable preferred stock, shares outstanding	6,111,000	6,361,000
Mandatory redemption and aggregate liquidation value, redeemable preferred stock	$ 305,550	$ 318,050
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	600,000,000	600,000,000
Common stock, shares issued	284,449,372	290,826,284
Common stock, shares outstanding	284,449,372	290,826,284