Retirement Plans - Schedule of Amounts Recognized as Other Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Compensation and Retirement Disclosure [Abstract]
Amounts Recognized in the Statement of Financial Condition as Other liabilities	$ 1,822	$ 1,644

This represents the entire liability recognized in the balance sheet that is associated with the defined benefit pension plans.

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Name:	us-gaap_DefinedBenefitPensionPlanCurrentAndNoncurrentLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant