Summary of Significant Accounting Policies - AOCI (Details) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended										6 Months Ended		9 Months Ended		12 Months Ended				18 Months Ended	21 Months Ended
		Dec. 31, 2015		Oct. 04, 2015	Jul. 04, 2015		Mar. 31, 2015		Dec. 31, 2014	Sep. 28, 2014	Jun. 29, 2014	Oct. 04, 2015		Dec. 31, 2015		Mar. 31, 2015		Mar. 31, 2014		Sep. 28, 2014	Dec. 31, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning of period unrealized gain (loss) in AOCI		$ (813,594)			$ (847,648)	[1]			$ (656,538)	$ (662,219)	$ (680,809)	$ (847,648)	[1]	$ (847,648)	[1]	$ (680,809)
Net decrease in fair value of derivatives														(5,654)		(8,097)
Net losses reclassified from AOCI, offsetting the price paid to suppliers														4,668		11,046
Net losses reclassified from AOCI, due to ineffectiveness														0		0
Net actuarial losses reclassified from AOCI	[2]													70,550		13,841		$ 91,387
Prior service costs reclassified from AOCI	[2]													(13,004)		(18,906)		(18,125)
Valuation adjustment for pension and postretirement benefit plans	[2]													4,805		(224,389)		78,522
Net change in cumulative translation adjustment	[2]													0		(36,796)		(1,505)
Other														375		238
Distribution of Sporting														0		96,224
End of period unrealized gain (loss) in AOCI		$ (785,908)	[1]	$ (813,594)			$ (847,648)	[1]		$ (656,538)	$ (662,219)	$ (813,594)		(785,908)	[1]	(847,648)	[1]	(680,809)		$ (656,538)
Ineffectiveness recognized in earnings														$ 0		$ 0		$ 0
Reconciliation of weighted-average outstanding shares used in calculation of basic earnings per share to diluted earnings per share
Weighted-average number of common shares outstanding, basic (in shares)		59,054		58,746	59,144		46,465		31,693	31,689	31,640	58,944		59,358	[2]	35,469	[2]	31,671	[2]	31,666	31,676
Dilutive effect of stock-based awards (in shares)														557		377		376
Dilutive effect of contingently issuable shares (in shares)														0		294		676
Weighted-average number of common shares outstanding, diluted (in shares)		59,574		59,304	59,749		46,928		31,998	32,058	33,108	59,526		59,915	[2]	36,140	[2]	32,723	[2]	32,605	32,410
Anti-dilutive stock options excluded from the calculation of diluted earnings per share (in shares)														91		73		45
Derivatives
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning of period unrealized gain (loss) in AOCI					$ (2,073)						$ (5,022)	$ (2,073)		$ (2,073)		$ (5,022)
Net decrease in fair value of derivatives														(5,654)		(8,097)
Net losses reclassified from AOCI, offsetting the price paid to suppliers														4,668		11,046
Net losses reclassified from AOCI, due to ineffectiveness														0		0
End of period unrealized gain (loss) in AOCI		$ (3,059)					$ (2,073)							(3,059)		(2,073)		$ (5,022)
Pension and Other Post- retirement Benefits
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning of period unrealized gain (loss) in AOCI					(846,645)						(675,114)	(846,645)		(846,645)		(675,114)
Net actuarial losses reclassified from AOCI														(70,550)		13,841
Prior service costs reclassified from AOCI														(13,004)		(18,906)
Valuation adjustment for pension and postretirement benefit plans														4,805		(224,389)
Distribution of Sporting														0		57,923
End of period unrealized gain (loss) in AOCI		(784,294)					(846,645)							(784,294)		(846,645)		(675,114)
Available-for-sale Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning of period unrealized gain (loss) in AOCI					1,070						832	1,070		1,070		832
Other														375		238
End of period unrealized gain (loss) in AOCI		$ 1,445					1,070							1,445		1,070		832
Cumulative Translation Adjustment
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning of period unrealized gain (loss) in AOCI					$ 0						$ (1,505)	$ 0		$ 0		(1,505)
Net change in cumulative translation adjustment																(36,796)
Distribution of Sporting																38,301
End of period unrealized gain (loss) in AOCI							$ 0									$ 0		$ (1,505)

[1] See Note 2 - Restatement

[2] See Note 2 - Restatement