Consolidating Financial Statements Condensed Consolidating Statements of Income and Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Income Statement [Abstract]
SALES	$ 393,719	$ 336,571
Cost of sales	266,018	235,708
Selling and general expenses	16,099	19,265
Other operating (income) expense, net	(3,503)	(1,139)
Costs and Expenses, Total	278,614	253,834
Equity in income (loss) of New Zealand joint venture	258	13
OPERATING (LOSS) INCOME	115,363	82,750
Interest Expense	(7,717)	(11,825)
Interest and miscellaneous income (expense), net	57	(23)
Equity in income from subsidiaries	0	0
INCOME BEFORE INCOME TAXES	107,703	70,902
Income tax benefit (expense)	(4,445)	(18,303)
Income (Loss) from Continuing Operations Attributable to Parent	103,258	52,599
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	44,477	838
NET INCOME	147,735	53,437	278,685
Foreign currency translation adjustment	975	5,825	4,352
New Zealand joint venture cash flow hedges	554	1,205	213
Gain from pension and postretirement plans, net of income tax	4,969	3,140	(496)
Total other comprehensive income	6,498	10,170
COMPREHENSIVE INCOME	154,233	63,607
Parent Company [Member]
Income Statement [Abstract]
SALES	0	0
Cost of sales	0	0
Selling and general expenses	0	0
Other operating (income) expense, net	(1,881)	0
Costs and Expenses, Total	(1,881)	0
Equity in income (loss) of New Zealand joint venture	0	0
OPERATING (LOSS) INCOME	1,881	0
Interest Expense	(3,275)	(1,249)
Interest and miscellaneous income (expense), net	2,419	1,912
Equity in income from subsidiaries	146,710	52,774
INCOME BEFORE INCOME TAXES	147,735	53,437
Income tax benefit (expense)	0	0
Income (Loss) from Continuing Operations Attributable to Parent	147,735	53,437
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	0
NET INCOME	147,735	53,437
Foreign currency translation adjustment	975	5,825
New Zealand joint venture cash flow hedges	554	1,205
Gain from pension and postretirement plans, net of income tax	4,969	3,140
Total other comprehensive income	6,498	10,170
COMPREHENSIVE INCOME	154,233	63,607
Senior Exchangeable Notes due 2015 [Member] [Domain] | Guarantor Subsidiaries [Member]
Income Statement [Abstract]
SALES	0	0
Cost of sales	0	0
Selling and general expenses	2,401	3,311
Other operating (income) expense, net	523	121
Costs and Expenses, Total	2,924	3,432
Equity in income (loss) of New Zealand joint venture	0	0
OPERATING (LOSS) INCOME	(2,924)	(3,432)
Interest Expense	(252)	(238)
Interest and miscellaneous income (expense), net	529	1,327
Equity in income from subsidiaries	148,765	55,446
INCOME BEFORE INCOME TAXES	146,118	53,103
Income tax benefit (expense)	592	(329)
Income (Loss) from Continuing Operations Attributable to Parent	146,710	52,774
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	0
NET INCOME	146,710	52,774
Foreign currency translation adjustment	975	5,825
New Zealand joint venture cash flow hedges	554	1,205
Gain from pension and postretirement plans, net of income tax	4,969	3,140
Total other comprehensive income	6,498	10,170
COMPREHENSIVE INCOME	153,208	62,944
Senior Exchangeable Notes due 2015 [Member] [Domain] | Consolidation, Eliminations [Member]
Income Statement [Abstract]
SALES	0	0
Cost of sales	0	0
Selling and general expenses	0	0
Other operating (income) expense, net	0	0
Costs and Expenses, Total	0	0
Equity in income (loss) of New Zealand joint venture	0	0
OPERATING (LOSS) INCOME	0	0
Interest Expense	0	0
Interest and miscellaneous income (expense), net	0	0
Equity in income from subsidiaries	(418,944)	(153,965)
INCOME BEFORE INCOME TAXES	(418,944)	(153,965)
Income tax benefit (expense)	0	0
Income (Loss) from Continuing Operations Attributable to Parent	(418,944)	(153,965)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	0
NET INCOME	(418,944)	(153,965)
Foreign currency translation adjustment	(2,190)	(11,548)
New Zealand joint venture cash flow hedges	(1,108)	(2,410)
Gain from pension and postretirement plans, net of income tax	(8,981)	(7,900)
Total other comprehensive income	(12,279)	(21,858)
COMPREHENSIVE INCOME	(431,223)	(175,823)
Senior Exchangeable Notes due 2015 [Member] [Domain] | Subsidiary Issuer [Member]
Income Statement [Abstract]
SALES	0	0
Cost of sales	0	0
Selling and general expenses	0	0
Other operating (income) expense, net	0	0
Costs and Expenses, Total	0	0
Equity in income (loss) of New Zealand joint venture	0	0
OPERATING (LOSS) INCOME	0	0
Interest Expense	(6,618)	(10,226)
Interest and miscellaneous income (expense), net	(751)	(1,208)
Equity in income from subsidiaries	123,469	45,745
INCOME BEFORE INCOME TAXES	116,100	34,311
Income tax benefit (expense)	2,690	4,174
Income (Loss) from Continuing Operations Attributable to Parent	118,790	38,485
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	0
NET INCOME	118,790	38,485
Foreign currency translation adjustment	240	(102)
New Zealand joint venture cash flow hedges	0	0
Gain from pension and postretirement plans, net of income tax	4,012	2,380
Total other comprehensive income	4,252	2,278
COMPREHENSIVE INCOME	123,042	40,763
Senior Exchangeable Notes due 2015 [Member] [Domain] | Non-Guarantor Subsidiaries [Member]
Income Statement [Abstract]
SALES	393,719	336,571
Cost of sales	266,018	235,708
Selling and general expenses	13,698	15,954
Other operating (income) expense, net	(2,145)	(1,260)
Costs and Expenses, Total	277,571	250,402
Equity in income (loss) of New Zealand joint venture	258	13
OPERATING (LOSS) INCOME	116,406	86,182
Interest Expense	2,428	(112)
Interest and miscellaneous income (expense), net	(2,140)	(2,054)
Equity in income from subsidiaries	0	0
INCOME BEFORE INCOME TAXES	116,694	84,016
Income tax benefit (expense)	(7,727)	(22,148)
Income (Loss) from Continuing Operations Attributable to Parent	108,967	61,868
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	44,477	838
NET INCOME	153,444	62,706
Foreign currency translation adjustment	975	5,825
New Zealand joint venture cash flow hedges	554	1,205
Gain from pension and postretirement plans, net of income tax	0	2,380
Total other comprehensive income	1,529	9,410
COMPREHENSIVE INCOME	154,973	72,116
Senior Notes due 2022 at a fixed interest rate of 3.75% [Member] | Guarantor Subsidiaries [Member]
Income Statement [Abstract]
SALES	0	0
Cost of sales	0	0
Selling and general expenses	2,401	3,311
Other operating (income) expense, net	523	121
Costs and Expenses, Total	2,924	3,432
Equity in income (loss) of New Zealand joint venture	0	0
OPERATING (LOSS) INCOME	(2,924)	(3,432)
Interest Expense	(6,870)	(10,464)
Interest and miscellaneous income (expense), net	(222)	119
Equity in income from subsidiaries	153,444	62,706
INCOME BEFORE INCOME TAXES	143,428	48,929
Income tax benefit (expense)	3,282	3,845
Income (Loss) from Continuing Operations Attributable to Parent	146,710	52,774
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	0
NET INCOME	146,710	52,774
Foreign currency translation adjustment	975	5,825
New Zealand joint venture cash flow hedges	554	1,205
Gain from pension and postretirement plans, net of income tax	4,969	3,140
Total other comprehensive income	6,498	10,170
COMPREHENSIVE INCOME	153,208	62,944
Senior Notes due 2022 at a fixed interest rate of 3.75% [Member] | Consolidation, Eliminations [Member]
Income Statement [Abstract]
SALES	0	0
Cost of sales	0	0
Selling and general expenses	0	0
Other operating (income) expense, net	0	0
Costs and Expenses, Total	0	0
Equity in income (loss) of New Zealand joint venture	0	0
OPERATING (LOSS) INCOME	0	0
Interest Expense	0	0
Interest and miscellaneous income (expense), net	0	0
Equity in income from subsidiaries	(300,154)	(115,480)
INCOME BEFORE INCOME TAXES	(300,154)	(115,480)
Income tax benefit (expense)	0	0
Income (Loss) from Continuing Operations Attributable to Parent	(300,154)	(115,480)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	0
NET INCOME	(300,154)	(115,480)
Foreign currency translation adjustment	(1,950)	(11,650)
New Zealand joint venture cash flow hedges	(1,108)	(2,410)
Gain from pension and postretirement plans, net of income tax	(4,969)	(5,520)
Total other comprehensive income	(8,027)	(19,580)
COMPREHENSIVE INCOME	(308,181)	(135,060)
Senior Notes due 2022 at a fixed interest rate of 3.75% [Member] | Non-Guarantor Subsidiaries [Member]
Income Statement [Abstract]
SALES	393,719	336,571
Cost of sales	266,018	235,708
Selling and general expenses	13,698	15,954
Other operating (income) expense, net	(2,145)	(1,260)
Costs and Expenses, Total	277,571	250,402
Equity in income (loss) of New Zealand joint venture	258	13
OPERATING (LOSS) INCOME	116,406	86,182
Interest Expense	2,428	(112)
Interest and miscellaneous income (expense), net	(2,140)	(2,054)
Equity in income from subsidiaries	0	0
INCOME BEFORE INCOME TAXES	116,694	84,016
Income tax benefit (expense)	(7,727)	(22,148)
Income (Loss) from Continuing Operations Attributable to Parent	108,967	61,868
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	44,477	838
NET INCOME	153,444	62,706
Foreign currency translation adjustment	975	5,825
New Zealand joint venture cash flow hedges	554	1,205
Gain from pension and postretirement plans, net of income tax	0	2,380
Total other comprehensive income	1,529	9,410
COMPREHENSIVE INCOME	$ 154,973	$ 72,116