Noncontrolling Interests (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Noncontrolling Interests
Revenues	$ 551,333,000	$ 431,842,000	$ 1,406,341,000	$ 1,060,851,000
Net income attributable to noncontrolling interests	1,348,000	432,000	1,947,000	600,000
Tax effect on income recognized	14,075,000	10,965,000	30,272,000	24,875,000
Accounts receivable	284,497,000		284,497,000		268,095,000
Current liabilities	410,633,000		410,633,000		420,669,000
Blythe joint venture | Primary beneficiary
Noncontrolling Interests
Revenues	15,468,000	7,750,000	47,371,000	13,164,000
Net income attributable to noncontrolling interests	1,348,000	432,000	1,947,000	600,000
Tax effect on income recognized			0
Distributions to noncontrolling interests			2,500,000	0
Distributions from joint venture			2,500,000	0
Capital contributions			0
Cash	1,793,000		1,793,000		3,565,000
Accounts receivable	8,448,000		8,448,000		8,843,000
Current liabilities	$ 8,318,000		$ 8,318,000		$ 9,379,000