Pensions, Other Post Retirement and Post Employment Benefits - Matching Contribution (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Contribution Plan Disclosure [Line Items]
Percentage contribution of compensation by eligible employees	99.00%
Percentage contribution by employer matching first condition of employee compensation	100.00%
Percentage of employee compensation matching under first condition	3.00%
Percentage contribution by employer matching second condition of employee compensation	50.00%
Percentage of employee compensation matching under second condition	2.00%
Matching contribution expense
Defined Contribution Plan Disclosure [Line Items]
Matching contribution expense	$ 1,209	$ 1,604	$ 1,684

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Defined Contribution Plan Expense

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Percentage Contribution By Employer Matching First Condition Of Employee Compensation

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Percentage Contribution By Employer Matching Second Condition Of Employee Compensation

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Percentage Contribution Of Compensation By Eligible Employees

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Percentage Of Employee Compensation Matching Under First Condition

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Percentage Of Employee Compensation Matching Under Second Condition

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