Employee Retirement and Postretirement Benefits - Components of Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Defined Benefit Plans
Components of net periodic benefit cost:
Service cost	$ 770	$ 923	$ 1,540	$ 1,846
Interest cost	3,495	3,128	6,990	6,256
Expected return on plan assets	(4,690)	(4,633)	(9,380)	(9,266)
Amortizations:
Unrecognized transition obligation	0	0	0	0
Prior service cost	197	198	394	396
Unrecognized net loss	1,276	3,098	2,552	6,196
Net periodic benefit cost	1,048	2,714	2,096	5,428
Postretirement Benefits
Components of net periodic benefit cost:
Service cost	206	204	412	408
Interest cost	416	306	832	612
Amortizations:
Prior service cost	16	6	32	12
Unrecognized net loss	19	75	38	150
Net periodic benefit cost	$ 657	$ 591	$ 1,314	$ 1,182