Employee Retirement and Postretirement Benefits - Components of Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Defined Benefit Plans
Components of net periodic benefit cost:
Service cost	$ 770	$ 923	$ 2,310	$ 2,769
Interest cost	3,495	3,128	10,485	9,384
Expected return on plan assets	(4,690)	(4,633)	(14,070)	(13,899)
Amortizations:
Prior service cost	197	198	591	594
Unrecognized net loss	1,276	3,098	3,828	9,294
Net periodic benefit cost	1,048	2,714	3,144	8,142
Postretirement Benefits
Components of net periodic benefit cost:
Service cost	206	204	618	612
Interest cost	416	306	1,248	918
Amortizations:
Prior service cost	16	6	48	18
Unrecognized net loss	19	75	57	225
Net periodic benefit cost	$ 657	$ 591	$ 1,971	$ 1,773