Pension and Other Postretirement Benefits - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined contribution expense	$ 13,500	$ 12,600	$ 11,800
Accumulated benefit obligation	253,900	272,500
Project benefit obligation for the pension plans with an accumulated benefit obligation in excess of plan assets	205,800	228,300
Accumulated benefit obligation for the pension plans with an accumulated benefit obligation in excess of assets	203,100	225,400
Fair value of plan assets for the pension plans with an accumulated benefit obligations in excess of plan assets	128,500	150,200
Projected benefit obligation of plan assets	50,700	46,900
Accumulated benefit obligation for the pension plans with an accumulated benefit obligation less than plan assets	50,700	47,100
Fair value of plan assets for the pension plans with an accumulated benefit obligations less than plan assets	$ 53,900	54,100
Target asset allocation for the investment of the assets in fixed income securities minimum	75.00%
Target asset allocation for the investment of the assets in fixed income securities maximum	80.00%
Target asset allocation for the investment of the assets in equity securities minimum	20.00%
Target asset allocation for the investment of the assets in equity securities maximum	25.00%
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation for the investment of the assets in fixed income securities	30.00%
Target asset allocation for the investment of the assets in equity securities	60.00%
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation for the investment of the assets in fixed income securities	40.00%
Target asset allocation for the investment of the assets in equity securities	70.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	$ 7,630	128	0
Pension and other postretirement plans	4,400
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	0	$ 0	$ 0
Pension and other postretirement plans	$ 1,800

Defined benefit plan accumulated other comprehensive income settlement loss.

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- Definition

Defined benefit plan pension plans with accumulated benefit obligations less than plan assets aggregate accumulated benefit obligation.

+ References

No definition available.

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- Definition

Defined benefit plan pension plans with accumulated benefit obligations less than plan assets aggregate fair value of plan assets.

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Defined benefit plan pension plans with accumulated benefit obligations less than plan assets aggregate projected benefit obligation.

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- Definition

Defined Benefit Plan Target Allocation Percentage Of Asset Equity Securities

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- Definition

Defined Benefit Plan Target Allocation Percentage Of Assets Debt Securities And Cash

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- Definition

Defined Benefit Plan Target Allocation Percentage Of Assets Debt Securities Range Maximum1

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Defined Benefit Plan Target Allocation Percentage Of Assets Debt Securities Range Minimum 1

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- Definition

For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Accumulated Benefit Obligation
-URI http://asc.fasb.org/extlink&oid=6503844

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

If aggregate disclosures are presented, the aggregate pension accumulated benefit obligation for pension plans with accumulated benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=73719040&loc=d3e4179-114921

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-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e2417-114920

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- Definition

If aggregate disclosures are presented, the aggregate fair value of plan assets for pension plans with accumulated benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.

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- Definition

If aggregate disclosures are presented, the aggregate projected benefit obligation for pension plans with accumulated benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
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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=65897934&loc=d3e1928-114920

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- Definition

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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
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-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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