Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Restricted cash and investments, current	$ 15,646	[1]	$ 15,654	[1]
Allowance for doubtful accounts	2,163		2,546
Restricted cash and investments, non-current	37,748		32,756
Property and equipment, net	1,739,986		1,687,159
Current portion of capital lease obligations, long-term debt and non-recourse debt	22,341		53,882
Non-recourse debt	93,352		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	86,589,630		86,007,433
Common stock, shares outstanding	72,003,856		71,417,034
Treasury stock, shares	14,585,774		14,590,399
Variable Interest Entity, Primary Beneficiary
Restricted cash and investments, current	6,308		6,182
Restricted cash and investments, non-current	16,943		15,521
Property and equipment, net	25,544		25,840
Current portion of capital lease obligations, long-term debt and non-recourse debt	5,450		5,200
Non-recourse debt	$ 11,588		$ 16,997

[1] Variable interest entities or “VIEs”