Summary of Transactions with FEI (Detail) (FEI Company, USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
FEI Company
Related Party Transaction [Line Items]
Equipment and services purchased from FEI	$ 36	$ 33	$ 37
Equipment sold to FEI	5
Due to FEI	10	8
Due from FEI	$ 0	$ 0

Amount for accounts payable to related parties.

For an unclassified balance sheet, amount of receivables arising from transactions with related parties.

Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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