Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Restricted cash and investments, current	$ 15,780	$ 15,654
Allowance for doubtful accounts	2,403	2,546
Restricted cash and investments, non-current	30,337	32,756
Property and equipment, net	1,680,165	1,687,159
Current portion of capital lease obligations, long-term debt and non-recourse debt	59,627	53,882
Non-recourse debt	97,964	104,836
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	30,000,000	30,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	90,000,000	90,000,000
Common stock, shares issued	86,188,835	86,007,433
Common stock, shares outstanding	71,600,440	71,417,034
Treasury stock, shares	14,588,395	14,590,399
Variable Interest Entity, Primary Beneficiary
Restricted cash and investments, current	6,308	6,182
Restricted cash and investments, non-current	8,916	15,521
Property and equipment, net	25,692	25,840
Current portion of capital lease obligations, long-term debt and non-recourse debt	5,450	5,200
Non-recourse debt	$ 11,569	$ 16,997