Changes in Benefit Obligations and Plan Assets as Well as Funded Status of Retirement Plans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Number Of Indexed Funds	6
Change in plan assets
Fair value of plan assets at end of year	$ 754,979	$ 691,063
Pension Benefits [Member]
Change in benefit obligation [Roll Forward]
Obligation at beginning of year	635,243	672,372
Service cost	13,529	15,834	14,788
Interest cost	29,757	26,791	27,363
Actuarial losses (gains)	104,374	(54,746)
Defined Benefit Plan, Business Combinations and Acquisitions, Benefit Obligation	11,080	0
Plan amendments	0	1,521
Benefits paid	(30,079)	(29,071)
Participants’ contributions	0	0
Foreign currency exchange rate changes	(7,734)	2,542
Obligation at end of year	756,170	635,243	672,372
Change in plan assets
Fair value of plan assets at beginning of year	691,063	633,261
Actual return on plan assets	83,120	85,809
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets	9,631
Employer contributions	1,244	1,064
Participants’ contributions	0	0
Benefits paid	(30,079)	(29,071)
Fair value of plan assets at end of year	754,979	691,063	633,261
Funded status	(1,191)	55,820
Amounts recognized in the consolidated balance sheets
Non-current assets	76,199	116,888
Current liabilities	(1,298)	(1,241)
Non-current liabilities	(76,092)	(59,827)
Net amount recognized	(1,191)	55,820
Amounts recognized in accumulated other comprehensive loss (income)
Net actuarial loss (gain)	152,480	75,539
Prior service cost (credit)	2,391	3,578
Net amount recognized	154,871	79,117
Other Postretirement Benefits [Member]
Change in benefit obligation [Roll Forward]
Obligation at beginning of year	36,505	49,177
Service cost	535	682	830
Interest cost	1,661	1,605	2,051
Actuarial losses (gains)	1,438	(10,352)
Defined Benefit Plan, Business Combinations and Acquisitions, Benefit Obligation	0	0
Plan amendments	(722)	(1,790)
Benefits paid	(2,893)	(3,714)
Participants’ contributions	904	897
Foreign currency exchange rate changes	0	0
Obligation at end of year	37,428	36,505	49,177
Change in plan assets
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	1,989	2,817
Participants’ contributions	904	897
Benefits paid	(2,893)	(3,714)
Fair value of plan assets at end of year	0	0	0
Funded status	(37,428)	(36,505)
Amounts recognized in the consolidated balance sheets
Non-current assets	0	0
Current liabilities	(3,094)	(3,291)
Non-current liabilities	(34,334)	(33,214)
Net amount recognized	(37,428)	(36,505)
Amounts recognized in accumulated other comprehensive loss (income)
Net actuarial loss (gain)	(3,357)	(5,124)
Prior service cost (credit)	(12,534)	(14,682)
Net amount recognized	$ (15,891)	$ (19,806)