Summary of Fair value of Plan Assets by Asset Category (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	$ 28,629		$ 24,590		$ 25,710
UNITED KINGDOM | Mutual Funds | Balanced Fund
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	14,266	[1]	12,353	[2]
UNITED KINGDOM | Mutual Funds | Growth Funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	14,244	[3]	12,136	[4]
UNITED KINGDOM | Cash
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	119		101
JAPAN
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	827		582		393
JAPAN | Insurance Contracts
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	827	[5]	582	[5]
Fair Value, Inputs, Level 1 | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	119		101
Fair Value, Inputs, Level 1 | UNITED KINGDOM | Cash
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	119		101
Fair Value, Inputs, Level 2 | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	28,510		24,489
Fair Value, Inputs, Level 2 | UNITED KINGDOM | Mutual Funds | Balanced Fund
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	14,266	[1]	12,353	[2]
Fair Value, Inputs, Level 2 | UNITED KINGDOM | Mutual Funds | Growth Funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	14,244	[3]	12,136	[4]
Fair Value, Inputs, Level 2 | JAPAN
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	827		582
Fair Value, Inputs, Level 2 | JAPAN | Insurance Contracts
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair Value of Plan Assets	$ 827	[5]	$ 582	[5]

[1] This class comprises a diversified portfolio of global investments which seeks a balanced return between capital growth and fixed income and is allocated on a weighted average basis as follows: equities (47%), debt (41%), other assets (9%) and cash (3%).

[2] This class comprises a diversified portfolio of global investments which seeks a balanced return between capital growth and fixed income and is allocated on a weighted average basis as follows: equities (40%), debt (36%), other assets (17%) and cash (7%).

[3] This class comprises a diversified portfolio of global investments which seeks long-term capital growth and is allocated on a weighted average basis as follows: equities (68%), other assets (10%), debt (21%), and cash (1%).

[4] This class comprises a diversified portfolio of global investments which seeks long-term capital growth and is allocated on a weighted average basis as follows: equities (60%), other assets (16%), debt (18%), and cash (6%).

[5] This class represents funds invested in insurance contracts.