Changes in Benefit Obligations and Plan Assets as Well as Funded Status of Retirement Plans (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) Investment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number Of Indexed Funds | Investment	6
Change in plan assets
Fair value of plan assets at beginning of year	$ 704,779
Fair value of plan assets at end of year	759,551	$ 704,779
Pension Benefits [Member]
Change in benefit obligation [Roll Forward]
Obligation at beginning of year	685,295	756,170
Service cost	12,895	15,562	$ 13,529
Interest cost	25,781	28,066	29,757
Actuarial losses (gains)	34,705	(73,890)
Special termination benefits	2,837	0
Plan amendments	472	23
Benefits paid	(33,492)	(32,316)
Curtailment gain	0	(522)
Participants’ contributions	0	0
Foreign currency exchange rate changes	(2,072)	(7,798)
Obligation at end of year	726,421	685,295	756,170
Change in plan assets
Fair value of plan assets at beginning of year	704,779	754,979
Actual return on plan assets	87,132	(19,054)
Employer contributions	1,132	1,170
Participants’ contributions	0	0
Benefits paid	(33,492)	(32,316)
Fair value of plan assets at end of year	759,551	704,779	754,979
Funded status	33,130	19,484
Amounts recognized in the consolidated balance sheets
Non-current assets	104,089	79,548
Current liabilities	(1,295)	(1,191)
Non-current liabilities	(69,664)	(58,873)
Net amount recognized	33,130	19,484
Amounts recognized in accumulated other comprehensive loss (income)
Net actuarial loss (gain)	148,941	151,872
Prior service cost (credit)	1,105	1,377
Net amount recognized	150,046	153,249
Other Postretirement Benefits [Member]
Change in benefit obligation [Roll Forward]
Obligation at beginning of year	28,022	37,428
Service cost	222	444	535
Interest cost	891	1,281	1,661
Actuarial losses (gains)	641	(5,018)
Special termination benefits	0	0
Plan amendments	(5,636)	(3,730)
Benefits paid	(3,007)	(3,243)
Curtailment gain	(305)	0
Participants’ contributions	870	860
Foreign currency exchange rate changes	0	0
Obligation at end of year	21,698	28,022	37,428
Change in plan assets
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	2,137	2,383
Participants’ contributions	870	860
Benefits paid	(3,007)	(3,243)
Fair value of plan assets at end of year	0	0	$ 0
Funded status	(21,698)	(28,022)
Amounts recognized in the consolidated balance sheets
Non-current assets	0	0
Current liabilities	(2,502)	(2,672)
Non-current liabilities	(19,196)	(25,350)
Net amount recognized	(21,698)	(28,022)
Amounts recognized in accumulated other comprehensive loss (income)
Net actuarial loss (gain)	(6,787)	(8,027)
Prior service cost (credit)	(14,753)	(13,207)
Net amount recognized	$ (21,540)	$ (21,234)