Cash Flow Disclosures (Cash Flow Activities) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Supplemental Quarterly Information [Abstract]
Decrease (increase) in accounts receivable	$ 284,542	$ (53,133)
Decrease (increase) in inventories	(25,547)	5,574
Increase in prepaid expenses	(40,191)	(41,191)
Decrease in deferred income tax assets	5,092	1,895
Increase (decrease) in accounts payable and accrued liabilities	(84,781)	55,729
Increase (decrease) in current income tax liabilities	(31,944)	79,575
Total	107,171	48,449
Cash income taxes paid, net of refunds	90,419	234,071
Interest paid, net of amounts capitalized	55,658	41,922
Asset retirement costs capitalized	6,703	12,985
Decrease in capital expenditure accrual	$ 336,952	$ 96,479