Pension Benefit and Retirement Health and Life Insurance Benefits (Additional Information) (Detail) (USD $)	3 Months Ended					12 Months Ended
	Dec. 31, 2014	Jun. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension and Other Postretirement Benefits Disclosure [Line Items]
Number of defined benefit pension plans	2					2
Projected benefit obligation of plan with accumulated benefit obligation in excess of plan assets	$ 155,200,000					$ 155,200,000	$ 144,300,000
Accumulated benefit obligation of plan with accumulated benefit obligation in excess of plan assets	155,200,000					155,200,000	144,300,000
Fair value of the plan assets of plan with accumulated benefit obligation in excess of plan assets	137,600,000					137,600,000	138,200,000
Projected benefit obligation of plan with plan assets in excess of accumulated benefit obligation	32,600,000					32,600,000	30,000,000
Accumulated benefit obligation of plan with plan assets in excess of accumulated benefit obligation	32,600,000					32,600,000	30,000,000
Fair value of the plan assets of plan with plan assets in excess of accumulated benefit obligation	33,000,000					33,000,000	33,000,000
Defined benefit plan, one-time cash payment				6,300,000
Change in discount rate						(0.75%)
Discount rate						4.00%	4.80%
Health care cost trend rate annual change						(0.50%)
Health care cost, employees age						65 years
Defined benefit pension plans, voluntary contributions						13,000,000	13,000,000
Estimated employer contributions in 2015						10,000,000
Equity Securities [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Plan asset allocations	23.00%					23.00%	60.00%
Debt Securities [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Plan asset allocations	77.00%					77.00%	40.00%
Retirees of 65 Years Old or Yonger [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Health care cost trend rate assumed for next fiscal year						7.50%	8.00%
Ultimate health care cost trend rate						4.50%
Retirees of 65 Years Old or Older [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Health care cost trend rate assumed for next fiscal year						7.50%	8.00%
Ultimate health care cost trend rate						4.50%
Retirement Health and Life Insurance Benefits [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Curtailment charges						0	0	0
Defined benefit plan, one-time cash payment						775,000	751,000
Net loss to be recognized over next twelve months						0
Settlement charge						0	0
Discount rate						3.25%	2.50%
Expected long-term rate of return on plan assets	0.00%					0.00%	0.00%
Defined benefit pension plans, voluntary contributions						775,000	751,000
Retirement Health and Life Insurance Benefits [Member] | Facility Closing [Member] | High Performance Foams [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Expenses and charges related to the termination of the operations			1,600,000					1,600,000
Pension Benefits [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Curtailment charges		1,500,000				0	(1,537,000)	0
Defined benefit plan, one-time cash payment						24,934,000	7,276,000
Net loss to be recognized over next twelve months						1,700,000
Settlement charge	5,200,000			2,100,000		0
Discount rate						4.75%	4.00%
Expected long-term rate of return on plan assets	6.50%					6.50%	7.50%
Defined benefit pension plans, voluntary contributions					$ 0	$ 13,871,000	$ 13,000,000