Other Comprehensive Income (Loss) (Accumulated Other Comprehensive Loss In Equity) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales and other revenues	$ 4,128,427	$ 3,080,483
Operating expenses	320,288	307,725
Interest expense	(32,723)	(27,158)
Income (loss) before income taxes	373,899	(54,571)
Income tax expense (benefit)	85,037	(16,789)
Net of tax and noncontrolling interest	268,091	(45,468)
Other comprehensive income (loss), net of tax	(10,008)	(2,438)
Foreign currency translation adjustment	4,965		$ 14,377
Unrealized loss on pension obligation	(692)		(654)
Unrealized gain on post-retirement benefit obligations	20,711		16,939
Unrealized loss on hedging instruments, net of noncontrolling interest	(5,123)		(793)
Accumulated other comprehensive income	19,861		$ 29,869
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive income (loss), net of tax	887	(392)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before income taxes	1,191	(631)
Income tax expense (benefit)	304	(247)
Net income	887	(384)
Noncontrolling interest	0	(8)
Net of tax and noncontrolling interest	887	(392)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Commodity Contract [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Sales and other revenues	1,647	3,950
Cost of Goods Sold	0	(299)
Operating expenses	(456)	(4,295)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Interest Rate Swap [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 0	$ 13