Pension Plans (Obligations and Funded Status) (Details) - USD ($) $ in Thousands			12 Months Ended
		Feb. 23, 2010	Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Service cost, plan formula, highest years calculated		5 years
Service cost, formula period		10 years
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Fair value of plan assets at beginning of year			$ 596,733
Fair value of plan assets at end of year			553,858		$ 596,733
Noncurrent liabilities			(158,984)		(141,546)
Qualified Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year			738,279		641,235
Service cost			14,131		11,759	$ 14,347
Interest cost			27,514		28,835	25,596
Actuarial liability (gain) loss	[1]		(36,245)		84,848
Benefit payments			(30,837)		(28,398)
Projected benefit obligation at end of year			712,842		738,279	641,235
Fair value of plan assets at beginning of year			596,733		555,400
Actual return on plan assets			(22,038)		59,731
Employer contributions			10,000		10,000
Fair value of plan assets at end of year			553,858		596,733	555,400
Funded status at end of year			(158,984)		(141,546)
Accumulated benefit obligation			712,842		738,279
Current liabilities			0	[2]	0
Noncurrent liabilities			(158,984)		(141,546)
Total			(158,984)		(141,546)
Unrecognized (gain) or loss			187,331		167,329
Unrecognized prior service cost (credit)			0		57
Amount included in accumulated other comprehensive income (loss)			187,331		167,386
Qualified pension plan and SERP that will be amortized from accumulated other comprehensive income (loss) in next fiscal year			12,500
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year			10,349		9,910
Service cost			206		256	340
Interest cost			318		342	311
Actuarial liability (gain) loss	[1]		(155)		660
Benefit payments			(534)		(819)
Projected benefit obligation at end of year			10,184		10,349	9,910
Fair value of plan assets at beginning of year			0		0
Actual return on plan assets			0		0
Employer contributions			534		819
Fair value of plan assets at end of year			0		0	$ 0
Funded status at end of year			(10,184)		(10,349)
Accumulated benefit obligation			10,184		10,349
Current liabilities			(530)		(531)
Noncurrent liabilities			(9,654)		(9,818)
Total			(10,184)		(10,349)
Unrecognized (gain) or loss			1,236		1,609
Unrecognized prior service cost (credit)			0		0
Amount included in accumulated other comprehensive income (loss)			1,236		$ 1,609
Qualified pension plan and SERP that will be amortized from accumulated other comprehensive income (loss) in next fiscal year			$ 200

[1] (a) The actuarial liability (gain)/loss amount for the qualified pension plan for 2015 and 2014 is principally due to the effect of changes in the discount rate.

[2] (a) The current liabilities are included in other accruals and payables on the Consolidated Balance Sheets