Other (Loss) Income, Net - Schedule of Other Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Long Lived Assets Held-for-sale [Line Items]
Interest income	$ 1,822us-gaap_InterestIncomeOperating	$ 1,142us-gaap_InterestIncomeOperating	$ 1,411us-gaap_InterestIncomeOperating
Gain on asset dispositions, net	2,094us-gaap_GainLossOnDispositionOfAssets1	436us-gaap_GainLossOnDispositionOfAssets1	8,396us-gaap_GainLossOnDispositionOfAssets1
Land impairment loss	(50)us-gaap_ImpairmentOfRealEstate	(1,557)us-gaap_ImpairmentOfRealEstate	0us-gaap_ImpairmentOfRealEstate
Escrow settlement	0msa_GainFromEscrowSettlement	0msa_GainFromEscrowSettlement	4,790msa_GainFromEscrowSettlement
Intangible asset impairment loss	0	0	(4,272)
Other, net	(1,101)us-gaap_OtherOperatingIncomeExpenseNet	(196)us-gaap_OtherOperatingIncomeExpenseNet	551us-gaap_OtherOperatingIncomeExpenseNet
Total	2,765us-gaap_OtherIncome	(175)us-gaap_OtherIncome	10,876us-gaap_OtherIncome
Detector Tube Assets
Long Lived Assets Held-for-sale [Line Items]
Gain on asset dispositions, net	$ 2,200

Gain From Escrow Settlement

No definition available.

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- Definition

Amount of gain (loss) on sale or disposal of assets, including but not limited to property plant and equipment, intangible assets and equity in securities of subsidiaries or equity method investee.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 45

-Paragraph 5

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- Definition

The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16373-109275

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- Definition

The charge against earnings in the period to reduce the carrying amount of real property to fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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-Paragraph 2

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- Definition

Amount of operating interest income, including, but not limited to, amortization and accretion of premiums and discounts on securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1(e))

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- Definition

Reflects the sum of all other revenue and income recognized by the entity in the period not otherwise specified in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.4)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 4

-Article 7

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- Definition

The net amount of other operating income and expenses, the components of which are not separately disclosed on the income statement, from items that are associated with the entity's normal revenue producing operations.

+ References

No definition available.

+ Details

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