Benefit Plans - Additional information (Detail) (USD $)	1 Months Ended			12 Months Ended					12 Months Ended							12 Months Ended					12 Months Ended
	Apr. 30, 2011	Jul. 31, 2010	Mar. 31, 2010	Dec. 31, 2012 Age CompensationPlan Employee	Dec. 31, 2011 CompensationPlan	Dec. 31, 2010	Dec. 31, 2012 Non Qualified Pension Plans CompensationPlan	Dec. 31, 2011 Non Qualified Pension Plans	Dec. 31, 2012 Non Qualified Pension Plans Fiscal Year 2013	Dec. 31, 2012 Equity Securities	Dec. 31, 2012 Debt Securities	Dec. 31, 2012 Specialty Investments	Dec. 31, 2012 Cash Reserves	Dec. 31, 2008 Investment At Westridge Capital Management	Apr. 30, 2011 Investment At Westridge Capital Management	Dec. 31, 2012 Pension Plans, Defined Benefit Y CompensationPlan	Dec. 31, 2011 Pension Plans, Defined Benefit	Dec. 31, 2010 Pension Plans, Defined Benefit	Dec. 31, 2012 Pension Plans, Defined Benefit Debt Securities	Dec. 31, 2011 Pension Plans, Defined Benefit Debt Securities	Dec. 31, 2012 Other Postretirement Benefit Plans, Defined Benefit	Dec. 31, 2011 Other Postretirement Benefit Plans, Defined Benefit	Dec. 31, 2010 Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Number of funded, noncontributory defined benefit pension plans																3
Normal retirement age																65
Projected benefit obligation							$ 92,322,000	$ 83,025,000								$ 991,338,000	$ 867,374,000	$ 761,384,000			$ 113,500,000	$ 134,926,000	$ 133,717,000
Number of unfunded, nonqualified pension plans							3
Accumulated benefit obligation							88,643,000	76,795,000								928,059,000	812,346,000
Estimated net actuarial loss expected to be amortized from accumulated other comprehensive income																26,216,000					2,331,000
Estimated prior service cost that will be amortized from accumulated other comprehensive income																380,000					(4,863,000)
Expected rate of return on plan assets				7.50%	8.00%											8.00%	8.00%	8.25%
Target allocation ranges for plan assets										50.00%	15.00%	10.00%	0.00%
Target allocation ranges for plan assets										77.00%	27.00%	20.00%	5.00%
Fair value of pension plan assets														59,245,000	11,227,000	683,091,000	636,648,000	630,303,000	155,874,000	152,240,000	0	0	0
Write-down in estimated fair value of assets														48,018,000
Partial distribution amount released by court-appointed receiver	22,041,000					6,555,000
Insurance settlement amount received by the Master Pension Trust related to the WCM loss						15,000,000
Return on plan assets	10,814,000															81,021,000	40,293,000				0	0
Total contributions (cash and stock) to pension plans		1,300,000	72,500,000
Contributions to pension plans in cash			18,636,000
Contributions to pension plans in stock			53,864,000
Number of shares contributed to pension plans			1,190,000
Value per share of shares contributed to pension plans			$ 45.26
Expected contributions to qualified and non-qualified pension plans				4,509,000	4,906,000	4,559,000			5,200,000
Percentage of contributions to individual multiemployer pension funds				5.00%	5.00%	5.00%
Percentage of domestic hourly labor force covered by collective bargaining agreements				20.00%
Percentage of domestic hourly labor force covered by collective bargaining agreements expiring in 2013				19.00%
Number of union employees in Mexico				235
Number of unfunded supplemental retirement plans				1	1
Accrued costs for the supplemental retirement plan				1,243,000	1,293,000
Eligibility age for early retirement coverage				62
Termination age for other group insurance coverage				65
Minimum discount rate				3.05%
Maximum discount rate				4.35%
Projected weighted average rate of compensation				3.50%												3.50%	3.50%	3.40%
Healthcare cost trend rate assumed for next year				8.00%																	8.00%	7.50%	8.00%
Ultimate health care cost trend rate				5.00%																	5.00%	5.00%	5.00%
Year reaching ultimate trend rate				2019																	2019	2017	2017
Number of defined contribution plans				3
Expense recognized relate to defined contribution plans				$ 18,460,000	$ 16,057,000	$ 15,273,000