Employee Benefit Plans (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Investment strategy mix, equity securities			55.00%
Investment strategy mix, real estate			3.00%
Investment strategy mix, fixed-income securities			42.00%
Overall expected long-term rate of return		7.65%
Estimated contributions to qualified pension plans		$ 51,000,000
Matching contribution by employer			50.00%
Deferred compensation expense					10,400,000
Income-tax charge as result of elimination of tax deduction	2,300,000
Change in the accumulated and projected benefit obligation			3,000,000
Long-term liabilities			610,850,000	418,731,000
Repurchased common stock issued under defined contribution plan			17,307,000	36,763,000	23,316,000
Treasury stock under primary defined contribution plan			461,151	1,130,515	733,219
Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Overall expected long-term rate of return			8.00%	8.50%	8.50%
Actuarial loss (gain)		19,300,000			(192,798,000)
Accrued liabilities			420,766,000	241,437,000
Long-term liabilities			420,766,000	241,437,000
Defined benefit plan employer contribution			62,615,000	93,761,000
Non-Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Overall expected long-term rate of return
Actuarial loss (gain)		900,000	7,587,000		(6,419,000)
Accrued liabilities			76,229,000	69,934,000
Long-term liabilities			71,178,000	65,177,000
Current portion of the obligation			5,051,000	4,757,000
Defined benefit plan employer contribution			5,079,000	4,947,000
Postretirement Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss (gain)			3,493,000	2,354,000	(10,353,000)
Accrued liabilities			98,417,000	92,993,000
Prior-service credits amortized		1,200,000	(1,212,000)	(1,202,000)	(1,222,000)
Long-term liabilities			91,595,000	86,230,000
Current portion of the obligation			6,822,000	6,763,000
Defined Contribution Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued liabilities			14,700,000	10,400,000
Defined benefit plan expense			$ 38,200,000	$ 36,700,000	$ 45,000,000
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Limited basic contribution in percentage			5.00%
Limited transition contribution in percentage			3.00%
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Limited basic contribution in percentage			3.00%
Limited transition contribution in percentage			1.00%
U.S. Large Companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment strategy mix, equity securities			27.00%
U.S. Small Companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment strategy mix, equity securities			8.00%
International [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment strategy mix, equity securities			20.00%