Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Restricted cash and investments, current	$ 9,337	[1]	$ 15,654	[1]
Allowance for doubtful accounts	1,891		2,546
Restricted cash and investments, non-current	24,303		32,756
Property and equipment, net	1,729,407		1,687,159
Current portion of capital lease obligations, long-term debt and non-recourse debt	17,120		53,882
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	86,637,734		86,007,433
Common stock, shares outstanding	72,054,307		71,417,034
Treasury stock, shares	14,583,427		14,590,399
Variable Interest Entity, Primary Beneficiary
Restricted cash and investments, current	0		6,182
Restricted cash and investments, non-current	0		15,521
Property and equipment, net	0		25,840
Current portion of capital lease obligations, long-term debt and non-recourse debt	0		5,200
Non-recourse debt	$ 0		$ 16,997

[1] Variable interest entities or “VIEs”