Financial Instruments and Risk Management (Derivative Instruments by Income Statement Location) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in OCI, tax	$ (6,660,000)	$ 40,720,000	$ 41,399,000
Deferred net gains (losses) on derivative instruments recorded in AOCI, net of tax, expected to be reclasses during next 12 months	13,400,000
Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss) recognized in OCI on derivative (effective portion), net of tax of ($6,660), $40,720 and $41,399	(10,866,000)	66,438,000	67,547,000
Designated as Hedging Instrument | Operating revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain reclassified from accumulated OCI into income (effective portion)	34,293,000	52,694,000	26,326,000
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	835,000	(5,340,000)	(2,767,000)
Not Designated as Hedging Instrument | Operating revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in income on derivative	$ (73,980,000)	$ 61,841,000	$ (37,587,000)