Amortization period of defined benefit plan assets gain loss.

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- Definition

Defined benefit plan assumptions used calculating net periodic benefit cost expected long term return on assets for next fiscal year.

+ References

No definition available.

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- Definition

Defined Benefit Plan Corridor Percentage

+ References

No definition available.

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- Definition

Defined benefit plan percentage of employer and related party securities included in plan assets.

+ References

No definition available.

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- Definition

Defined Contribution Plan, Number of Plans

+ References

No definition available.

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- Definition

Passive portfolio benchmark.

+ References

No definition available.

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- Definition

Pension benefits expected to be paid from employer assets.

+ References

No definition available.

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- Definition

Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level.

+ 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 (e)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

The amount of employer securities or securities of parties related to the employer that are included in plan assets.

+ 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 (n)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit 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 (a)
-URI http://asc.fasb.org/extlink&oid=82843861&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.

+ References

No definition available.

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- Definition

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ 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 (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

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- Definition

Percentage employer matches of the employee's percentage contribution matched.

+ References

No definition available.

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- Definition

Amount of dividend income on nonoperating 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 210.5-03.7(a))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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Employee Benefit Plans - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) plan	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Amortization period of plan assets gains and losses (in years)	5 years
Corridor percentage	10.00%
Benefit obligations	$ 2,435,765	$ 2,306,859	$ 2,199,356
Fair value of plan assets	2,206,479	1,965,502	1,912,736
Genuine Parts Company common stock included in equity securities	$ 191,771	$ 192,841
Genuine Parts Company common stock as a percentage of total plan assets	9.00%	10.00%
Dividend payments on Genuine Parts Company common stock received by plan	$ 5,450	$ 5,308
Expected rate of return on plan assets for measuring next fiscal year pension cost or income	7.20%
Pension benefits expected to be paid from employer assets in next fiscal year	$ 9,283
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of plans \| plan	1
Matching contribution to be received by pension plan participants of a specified percentage of employee's salary	100.00%
First percentage of employee's salary out of which matching contribution will be made	5.00%
Total defined contribution plans expense	$ 58,186	56,975	$ 55,066
Canada [Member]
Defined Benefit Plan Disclosure [Line Items]
Matching contribution to be received by pension plan participants of a specified percentage of employee's salary	100.00%
First percentage of employee's salary out of which matching contribution will be made	5.00%
Total defined contribution plans expense	$ 2,600
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total accumulated benefit obligations	$ 2,409,091	2,281,648
Pension Plan [Member] \| S&P 500 Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	47.00%
Pension Plan [Member] \| Russell Mid Cap Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	5.00%
Pension Plan [Member] \| Russell 2000 Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	7.00%
Pension Plan [Member] \| MSCI EAFE Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	5.00%
Pension Plan [Member] \| DJ Global Moderate Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	5.00%
Pension Plan [Member] \| MSCI Emerging Market Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	3.00%
Pension Plan [Member] \| BarCap U.S. Govt/Credit [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	28.00%
Pension Plan [Member] \| United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations	$ 2,187,700	2,105,665
Fair value of plan assets	$ 1,969,196	$ 1,760,713