Noncontrolling Interests (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Noncontrolling Interests
Revenues	$ 445,013	$ 337,436	$ 855,008	$ 629,009
Net income attributable to noncontrolling interests	329	124	599	168
Tax effect on income recognized	9,990	7,346	16,197	13,910
Accounts receivable	251,092		251,092		268,095
Current liabilities	381,100		381,100		420,669
Blythe joint venture | Primary beneficiary
Noncontrolling Interests
Revenues	15,631	3,793	31,903	5,414
Net income attributable to noncontrolling interests	329	124	599	168
Tax effect on income recognized			0	0
Distributions to noncontrolling interests			0	0
Capital contributions made by noncontrolling interests			0	0
Cash	4,442		4,442		3,565
Accounts receivable	11,464		11,464		8,843
Current liabilities	$ 11,680		$ 11,680		$ 9,379