Consolidating Financial Statements Condensed Consolidating Statements of Income and Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended										12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement [Abstract]
SALES	$ 434,306	$ 408,988	$ 371,926	$ 355,780	$ 388,423		$ 385,091		$ 357,397	$ 357,731	$ 1,571,000	$ 1,488,642	$ 1,315,233
Costs and Expenses
Cost of sales											1,104,805	1,073,732	990,099
Selling and general expenses											68,397	66,541	67,102
Other operating expense (income), net											(13,103)	(3,829)	(10,519)
Costs and Expenses, Total											1,160,099	1,136,444	1,046,682
Equity in income (loss) of New Zealand joint venture											550	4,088	1,033
Operating Income Before Gain On Sale Of a Portion Of Interest In Joint Venture											411,451	356,286	269,584
Gain on sale of a portion of interest in New Zealand joint venture											0	0	12,367
Operating Income (Loss)	115,678	113,174	98,590	84,009	81,325	[1]	108,310		79,073	87,578	411,451	356,286	281,951
Interest expense											(44,981)	(50,775)	(50,463)
Interest and miscellaneous income (expense), net											606	851	1,315
Equity in income from subsidiaries											0	0	0
INCOME BEFORE INCOME TAXES											367,076	306,362	232,803
Income tax benefit (expense)											(88,391)	(30,357)	(15,217)
NET INCOME	75,609	80,560	69,079	53,437	56,230	[1]	104,909	[2]	56,454	58,412	278,685	276,005	217,586
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent											4,069	(45,090)	11,384
Comprehensive Income (Loss), Net of Tax, Attributable to Parent											282,754	230,915	228,970
Parent Company [Member]
Income Statement [Abstract]
SALES											0	0	0
Costs and Expenses
Cost of sales											0	0	0
Selling and general expenses											0	0	0
Other operating expense (income), net											110	0	0
Costs and Expenses, Total											110	0	0
Equity in income (loss) of New Zealand joint venture											0	0	0
Operating Income Before Gain On Sale Of a Portion Of Interest In Joint Venture													0
Gain on sale of a portion of interest in New Zealand joint venture													0
Operating Income (Loss)											(110)	0	0
Interest expense											(10,717)	621	0
Interest and miscellaneous income (expense), net											6,638	0	0
Equity in income from subsidiaries											282,874	275,384	217,586
INCOME BEFORE INCOME TAXES											278,685	276,005	217,586
Income tax benefit (expense)											0	0	0
NET INCOME											278,685	276,005	217,586
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent											4,069	(45,090)	11,384
Comprehensive Income (Loss), Net of Tax, Attributable to Parent											282,754	230,915	228,970
Senior Exchangeable Notes due 2012 & 2015 [Member] | Guarantor Subsidiaries [Member]
Income Statement [Abstract]
SALES											0	0	0
Costs and Expenses
Cost of sales											0	0	0
Selling and general expenses											10,575	10,710	10,122
Other operating expense (income), net											962	117	385
Costs and Expenses, Total											11,537	10,827	10,507
Equity in income (loss) of New Zealand joint venture											0	0	0
Operating Income Before Gain On Sale Of a Portion Of Interest In Joint Venture													(10,507)
Gain on sale of a portion of interest in New Zealand joint venture													0
Operating Income (Loss)											(11,537)	(10,827)	(10,507)
Interest expense											(941)	(1,133)	239
Interest and miscellaneous income (expense), net											5,519	5,280	12,952
Equity in income from subsidiaries											289,486	281,892	221,578
INCOME BEFORE INCOME TAXES											282,527	275,212	224,262
Income tax benefit (expense)											347	172	(6,676)
NET INCOME											282,874	275,384	217,586
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent											4,069	(45,090)	11,384
Comprehensive Income (Loss), Net of Tax, Attributable to Parent											286,943	230,294	228,970
Senior Exchangeable Notes due 2012 & 2015 [Member] | Issuer Subsidiary [Member]
Income Statement [Abstract]
SALES											0	0	0
Costs and Expenses
Cost of sales											0	0	0
Selling and general expenses											0	0	0
Other operating expense (income), net											0	0	0
Costs and Expenses, Total											0	0	0
Equity in income (loss) of New Zealand joint venture											0	0	0
Operating Income Before Gain On Sale Of a Portion Of Interest In Joint Venture													0
Gain on sale of a portion of interest in New Zealand joint venture													0
Operating Income (Loss)											0	0	0
Interest expense											(37,971)	(49,555)	(50,313)
Interest and miscellaneous income (expense), net											(3,334)	(4,508)	(4,309)
Equity in income from subsidiaries											232,871	170,048	137,471
INCOME BEFORE INCOME TAXES											191,566	115,985	82,849
Income tax benefit (expense)											15,076	19,733	19,937
NET INCOME											206,642	135,718	102,786
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent											(453)	(35,712)	4,056
Comprehensive Income (Loss), Net of Tax, Attributable to Parent											206,189	100,006	106,842
Senior Exchangeable Notes due 2012 & 2015 [Member] | Non-Guarantor Subsidiaries [Member]
Income Statement [Abstract]
SALES											1,571,000	1,488,642	1,315,233
Costs and Expenses
Cost of sales											1,104,805	1,073,732	990,099
Selling and general expenses											57,822	55,831	56,980
Other operating expense (income), net											(14,175)	(3,946)	(10,904)
Costs and Expenses, Total											1,148,452	1,125,617	1,036,175
Equity in income (loss) of New Zealand joint venture											550	4,088	1,033
Operating Income Before Gain On Sale Of a Portion Of Interest In Joint Venture													280,091
Gain on sale of a portion of interest in New Zealand joint venture													12,367
Operating Income (Loss)											423,098	367,113	292,458
Interest expense											4,648	(708)	(389)
Interest and miscellaneous income (expense), net											(8,217)	79	(7,328)
Equity in income from subsidiaries											0	0	0
INCOME BEFORE INCOME TAXES											419,529	366,484	284,741
Income tax benefit (expense)											(103,814)	(50,262)	(28,478)
NET INCOME											315,715	316,222	256,263
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent											4,116	(34,403)	8,967
Comprehensive Income (Loss), Net of Tax, Attributable to Parent											319,831	281,819	265,230
Senior Exchangeable Notes due 2012 & 2015 [Member] | Consolidation, Eliminations [Member]
Income Statement [Abstract]
SALES											0	0	0
Costs and Expenses
Cost of sales											0	0	0
Selling and general expenses											0	0	0
Other operating expense (income), net											0	0	0
Costs and Expenses, Total											0	0	0
Equity in income (loss) of New Zealand joint venture											0	0	0
Operating Income Before Gain On Sale Of a Portion Of Interest In Joint Venture													0
Gain on sale of a portion of interest in New Zealand joint venture													0
Operating Income (Loss)											0	0	0
Interest expense											0	0	0
Interest and miscellaneous income (expense), net											0	0	0
Equity in income from subsidiaries											(805,231)	(727,324)	(576,635)
INCOME BEFORE INCOME TAXES											(805,231)	(727,324)	(576,635)
Income tax benefit (expense)											0	0	0
NET INCOME											(805,231)	(727,324)	(576,635)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent											(7,732)	115,205	(24,407)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent											(812,963)	(612,119)	(601,042)
Senior Notes due 2022 at a fixed interest rate of 3.75% [Member] | Guarantor Subsidiaries [Member]
Income Statement [Abstract]
SALES											0	0	0
Costs and Expenses
Cost of sales											0	0	0
Selling and general expenses											10,575	10,710	10,122
Other operating expense (income), net											962	117	385
Costs and Expenses, Total											11,537	10,827	10,507
Equity in income (loss) of New Zealand joint venture											0	0	0
Operating Income Before Gain On Sale Of a Portion Of Interest In Joint Venture													(10,507)
Gain on sale of a portion of interest in New Zealand joint venture													0
Operating Income (Loss)											(11,537)	(10,827)	(10,507)
Interest expense											(38,912)	(50,688)	(50,074)
Interest and miscellaneous income (expense), net											2,185	772	8,643
Equity in income from subsidiaries											315,715	316,222	256,263
INCOME BEFORE INCOME TAXES											267,451	255,479	204,325
Income tax benefit (expense)											15,423	19,905	13,261
NET INCOME											282,874	275,384	217,586
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent											4,069	(45,090)	11,384
Comprehensive Income (Loss), Net of Tax, Attributable to Parent											286,943	230,294	228,970
Senior Notes due 2022 at a fixed interest rate of 3.75% [Member] | Non-Guarantor Subsidiaries [Member]
Income Statement [Abstract]
SALES											1,571,000	1,488,642	1,315,233
Costs and Expenses
Cost of sales											1,104,805	1,073,732	990,099
Selling and general expenses											57,822	55,831	56,980
Other operating expense (income), net											(14,175)	(3,946)	(10,904)
Costs and Expenses, Total											1,148,452	1,125,617	1,036,175
Equity in income (loss) of New Zealand joint venture											550	4,088	1,033
Operating Income Before Gain On Sale Of a Portion Of Interest In Joint Venture													280,091
Gain on sale of a portion of interest in New Zealand joint venture													12,367
Operating Income (Loss)											423,098	367,113	292,458
Interest expense											4,648	(708)	(389)
Interest and miscellaneous income (expense), net											(8,217)	79	(7,328)
Equity in income from subsidiaries											0	0	0
INCOME BEFORE INCOME TAXES											419,529	366,484	284,741
Income tax benefit (expense)											(103,814)	(50,262)	(28,478)
NET INCOME											315,715	316,222	256,263
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent											4,116	(34,403)	8,967
Comprehensive Income (Loss), Net of Tax, Attributable to Parent											319,831	281,819	265,230
Senior Notes due 2022 at a fixed interest rate of 3.75% [Member] | Consolidation, Eliminations [Member]
Income Statement [Abstract]
SALES											0	0	0
Costs and Expenses
Cost of sales											0	0	0
Selling and general expenses											0	0	0
Other operating expense (income), net											0	0	0
Costs and Expenses, Total											0	0	0
Equity in income (loss) of New Zealand joint venture											0	0	0
Operating Income Before Gain On Sale Of a Portion Of Interest In Joint Venture													0
Gain on sale of a portion of interest in New Zealand joint venture													0
Operating Income (Loss)											0	0	0
Interest expense											0	0	0
Interest and miscellaneous income (expense), net											0	0	0
Equity in income from subsidiaries											(598,589)	(591,606)	(473,849)
INCOME BEFORE INCOME TAXES											(598,589)	(591,606)	(473,849)
Income tax benefit (expense)											0	0	0
NET INCOME											(598,589)	(591,606)	(473,849)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent											(8,185)	79,493	(20,351)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent											$ (606,774)	$ (512,113)	$ (494,200)

[1] Fourth quarter 2011 included a pre-tax expense of $6.5 million ($4.1 million after tax) due to an increase in a disposition reserve.

[2] Third quarter 2011 included a benefit of $16.0 million from the reversal of a reserve related to the taxability of the AFMC.