Benefit Obligations - Change in Benefit Obligation (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at January 1	$ 1,463,079		$ 1,331,137
Service cost	415		531		472
Interest cost	61,456		67,499		70,337
Actuarial loss/(gain)	113,770		150,776
Benefits paid	(87,304)	[1]	(86,659)	[1]
Curtailments and foreign exchange impact	77		(205)
Projected benefit obligation at December 31	1,551,493		1,463,079		1,331,137
Post-retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at January 1	57,934		44,488
Service cost	89		75		81
Interest cost	2,600		2,597		2,441
Actuarial loss/(gain)	(1,973)		11,893
Benefits paid	(1,266)	[1]	(1,119)	[1]
Curtailments and foreign exchange impact
Projected benefit obligation at December 31	$ 57,384		$ 57,934		$ 44,488

[1] The pension benefits paid include amounts paid under certain international pension plans, which do not maintain plan assets.