Amortization period of defined benefit plan assets gain loss.

No definition available.

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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, Benefit Obligation, Actuarial Gain (Loss), Discount Rate Change

+ 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.

+ Details

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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

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- Definition

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

+ References

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- Definition

Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

+ References

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- Definition

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

+ References

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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

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
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- Definition

Amount of increase in benefit obligation for benefits provided to employees payable from defined benefit plan or payable upon retirement.

+ References

+ Details

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- Definition

Amount of cost for defined contribution plan.

+ References

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-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
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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.

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Employee Benefit Plans - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) plan	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Amortization period of plan assets gains and losses (in years)	5 years
Benefit obligations	$ 2,678,966	$ 2,496,600	$ 2,278,043
Total accumulated benefit obligations	2,649,418	2,466,322
Actuarial loss	218,534	246,352
Actual return on plan assets	347,560	427,597
Special termination costs	0	42,757
Fair value of plan assets	$ 2,545,359	$ 2,311,227	2,043,379
Genuine Parts Company common stock as a percentage of total plan assets	8.00%	9.00%
Dividend payments on Genuine Parts Company common stock received by plan	$ 6,378	$ 6,156
Expected rate of return on plan assets for measuring next fiscal year pension cost or income	6.88%
Pension benefits expected to be paid from employer assets in next fiscal year	$ 17,574
United States
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations	2,373,884	2,228,066
Fair value of plan assets	$ 2,258,246	2,051,474
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	$ 54,885	64,990	$ 62,335
United States \| U.S. Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	175,200
Actual return on plan assets	184,200
Loss from discount rate change	173,000
United States \| U.S. Supplemental Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	20,300
Loss from discount rate change	$ 21,400
Canada
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	$ 4,486	4,433
S&P 500 Index
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	47.00%
Russell Mid Cap Index
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	5.00%
Russell 2000 Index
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	7.00%
MSCI EAFE Index
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	5.00%
DJ Global Moderate Index
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	5.00%
MSCI Emerging Market Net
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	3.00%
BarCap U.S. Govt/Credit
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	28.00%
Genuine Parts Company common stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 202,711	$ 214,418