Pension Benefit and Retirement Health and Life Insurance Benefits (Additional Information) (Detail) (USD $)	12 Months Ended				3 Months Ended	12 Months Ended												3 Months Ended		12 Months Ended			6 Months Ended	12 Months Ended			3 Months Ended	12 Months Ended					12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Sep. 30, 2012	Dec. 31, 2012 President and Chief Executive Officer [Memeber]	Dec. 31, 2012 Equity Securities [Member]	Dec. 31, 2012 Debt Securities [Member]	Dec. 31, 2012 Retirees of 65 Years Old or Yonger [Member]	Dec. 31, 2011 Retirees of 65 Years Old or Yonger [Member]	Dec. 31, 2012 Retirees of 65 Years Old or Older [Member]	Dec. 31, 2011 Retirees of 65 Years Old or Older [Member]	Dec. 31, 2013 Voluntary Contributions [Member]	Dec. 31, 2012 Voluntary Contributions [Member]	Dec. 31, 2011 Voluntary Contributions [Member]	Dec. 31, 2012 Retirement Health and Life Insurance Benefits [Member]	Dec. 31, 2011 Retirement Health and Life Insurance Benefits [Member]	Dec. 31, 2010 Retirement Health and Life Insurance Benefits [Member]	Dec. 31, 2012 Pension Benefits [Member]	Sep. 30, 2011 Pension Benefits [Member]	Dec. 31, 2012 Pension Benefits [Member]	Dec. 31, 2011 Pension Benefits [Member]	Dec. 31, 2010 Pension Benefits [Member]	Jun. 30, 2012 High Performance Foams [Member]	Dec. 31, 2012 High Performance Foams [Member]	Dec. 31, 2011 High Performance Foams [Member]	Dec. 31, 2010 High Performance Foams [Member]	Mar. 31, 2012 High Performance Foams [Member] Facility Closing [Member] Retirement Health and Life Insurance Benefits [Member]	Dec. 31, 2012 Rate of return on plan assets over the next 7 year period [Member]	Dec. 31, 2012 Rate of return on plan assets over the next 5 year period [Member]	Dec. 31, 2012 Hypothetical rates of return on plan assets for a 10 year period [Member]	Dec. 31, 2012 Hypothetical rates of return on plan assets for a 20 year period [Member]	Dec. 31, 2012 Historical performance of plan assets over a 16 year period [Member]	Dec. 31, 2012 Hypothetical rates of return on plan assets for a 30 year period [Member]	Dec. 31, 2012 Fixed Income Securities [Member] Rate of return on plan assets over the next 7 year period [Member]	Dec. 31, 2012 Fixed Income Securities [Member] Rate of return on plan assets over the next 5 year period [Member]	Dec. 31, 2012 Equity Securities [Member] Rate of return on plan assets over the next 7 year period [Member]	Dec. 31, 2012 Equity Securities [Member] Rate of return on plan assets over the next 5 year period [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Plan amendment, employees impacted, maximum age															50 years
Defined Benefit Plan, Plan Amendment, Employees Impacted, Age 50 or less															less than age 50
Expenses and charges related to the termination of the operations																							$ 861,000	$ 861,000	$ 0	$ 0	$ (1,593,000)
Projected benefit obligation of plan assets with accumulated benefit obligation in excess of plan assets	209,800,000	193,700,000
Accumulated benefit obligation of plan assets with accumulated benefit obligation in excess of plan assets	186,100,000	172,400,000
Fair value of plan assets with accumulated benefit obligation in excess of plan assets	143,500,000	120,600,000
Defined benefit plan, one-time cash payment					6,300,000										795,000	877,000				6,800,000	6,874,000
Settlement charge																		2,073,000		(6,723,000)
Estimated net loss to be amortized from other comprehensive income into net periodic benefit cost over the next fiscal year															500,000					5,900,000
Prior service cost to be amortized from other comprehensive income into net periodic benefit cost over the next fiscal year															(500,000)					400,000
Change in discount rate		(0.50%)
Discount rate	4.50%	4.00%													3.50%	4.50%				4.50%	5.50%
Health care cost trend rate assumed for next fiscal year								8.00%	7.00%	7.50%	8.50%
Ultimate health care cost trend rate								5.00%		5.50%
Percentage point change in assumed health care cost trend rates	100.00%
Health care cost, employees age	65 years
Target plan asset allocations						57.00%	43.00%
Defined Benefit Plan, Expected Return on Plan Assets	0.086														0	0	0			9,892,000	10,559,000	9,628,000						0.078	0.073	0.080	0.081		0.102	0.045	0.035	0.110	0.095
Number Of Years	1 year 6 months			5 years																								15 years	10 years	10 years	20 years	16 years	30 years
Defined benefit pension plans, voluntary contributions	$ 1,700,000	$ 1,700,000	$ 1,500,000									$ 13,000,000	$ 16,000,000	$ 5,000,000	$ 795,000	$ 877,000		$ 0	$ 0	$ 22,723,000	$ 5,027,000