Employee Benefit Plans - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation And Retirement Disclosure [Abstract]
Defined contribution pension plans	$ 2,400,000	$ 2,100,000	$ 1,900,000
Average annual rate of return (including the CMRT's investment in TIMET common stock)		14.00%nl_ActualRateOfReturnOnCmrtAssets
Long-term return on plan assets	7.20%	9.20%	9.20%
Weighted average discount rate	4.50%	3.70%	4.30%
CMRT
Compensation And Retirement Disclosure [Abstract]
Percentage of assets valued using observable inputs from level one or level two	80.00%	83.00%
Defined Benefit Pension Plans
Compensation And Retirement Disclosure [Abstract]
Expected contributions for pension plans in 2015	800,000
Actuarial losses expected to be recognized as a component of net period cost in next fiscal year	1,300,000
Weighted-average rate determining the actuarial present value of benefit obligation	3.80%	4.50%
Net actuarial gain (loss)	(8,585,000)	3,696,000
Defined Benefit Pension Plans \| CMRT
Compensation And Retirement Disclosure [Abstract]
Long-term return on plan assets		10.00%	10.00%
Long-term return on plan assets next twelve months	7.50%
OPEB
Compensation And Retirement Disclosure [Abstract]
Expected contributions for pension plans in 2015	500,000
Weighted-average rate determining the actuarial present value of benefit obligation	3.00%	3.20%
Eligible age for health care benefits	65 years
Net actuarial gain (loss)	(385,000)	240,000
Weighted average discount rate	3.20%	2.50%	3.30%
OPEB \| Scenario Forecast
Compensation And Retirement Disclosure [Abstract]
Net actuarial gain (loss)	100,000
Prior service credit	$ 600,000

Actual rate of return on cmrt assets.

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- Definition

Defined benefit plan assumptions used calculating net periodic benefit cost expected long term return on assets next twelve months.

+ References

No definition available.

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- Definition

Percentage of assets valued using observable inputs from level one or level two.

+ References

No definition available.

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- Definition

Reduced health benefit eligibility age.

+ References

No definition available.

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- Definition

Amount of gain (loss) related to change in benefit obligation resulting from changes in actuarial assumptions, for example, but not limited to, interest, mortality, employee turnover, salary, and temporary deviation from the substantive plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Gain or Loss

-URI http://asc.fasb.org/extlink&oid=6514294

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(4)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Glossary Gain or Loss

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- Definition

The interest rate used to adjust for the time value of money for the plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(1)

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- Definition

The interest rate used to adjust for the time value of money.

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- Definition

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Long-Term Rate of Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512013

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-Subparagraph (k)(3)

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- Definition

Amount included in accumulated other comprehensive income (AOCI) related to gain (loss) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position.

+ References

No definition available.

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- Definition

Amount included in accumulated other comprehensive income (AOCI) related to prior service cost (credit) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position.

+ References

No definition available.

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- Definition

Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

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