Acquisitions (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		4 Months Ended	9 Months Ended
	May. 24, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	May. 23, 2015	Dec. 31, 2014
Assets:
Goodwill		$ 150,032		$ 150,032	$ 150,032			$ 173,928
Liabilities:
Accrued liabilities		22,278		22,278	22,278			$ 22,278
Operating revenues		847,553	$ 1,813,762		3,125,565	$ 5,020,361
Net income (loss)		$ (295,834)	$ 106,048		(209,021)	220,411
Joint Venture in Saudi Arabia
Acquisitions
Ownership percentage							51.00%
Carrying value of equity method investment							$ 44,700
Excess of fair value over carrying value of long-lived assets					2,300
Joint Venture in Saudi Arabia
Acquisitions
Cash paid for acquisitions of businesses	$ 106,000
Ownership percentage	49.00%
Assets:
Cash	$ 48,058
Accounts receivable	153,819
Other current assets	244,869
Property, plant and equipment, net	93,000
Intangible assets	12,400
Goodwill	58,663
Other long-term assets	287,138
Total assets	897,947
Liabilities:
Accounts payable	206,599
Accrued liabilities	236,700
Income taxes payable	8,500
Other long-term liabilities	293,167
Total liabilities	744,966
Net assets acquired	$ 152,981
Operating revenues				142,300
Net income (loss)				$ 6,200
Business Acquisition, Pro Forma Information
Total revenues and other income					3,268,546	5,173,745
Income (loss) from continuing operations, net of tax					$ (175,587)	$ 218,274
Income (loss) from continuing operations per share - basic					$ (0.61)	$ 0.72
Income (loss) from continuing operations per share - diluted					$ (0.61)	$ 0.72