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.

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- Definition

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

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- Definition

Defined Contribution Plan, Number of Plans

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- Definition

Passive portfolio benchmark.

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- Definition

Pension benefits expected to be paid from employer assets.

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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.

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- Definition

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

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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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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

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.

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- Definition

Amount of cost for defined contribution plan.

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

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

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Amount of dividend income on nonoperating securities.

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Employee Benefit Plans - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) plan	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Amortization period of plan assets gains and losses (in years)	5 years
Benefit obligations	$ 2,278,043	$ 2,435,765	$ 2,306,859
Total accumulated benefit obligations	2,247,013	2,409,091
Fair value of plan assets	$ 2,043,379	$ 2,206,479	1,965,502
Genuine Parts Company common stock as a percentage of total plan assets	9.00%	9.00%
Dividend payments on Genuine Parts Company common stock received by plan	$ 5,813	$ 5,450
Expected rate of return on plan assets for measuring next fiscal year pension cost or income	7.12%
Pension benefits expected to be paid from employer assets in next fiscal year	$ 9,215
Employer contributions	$ 57,549	53,309
S&P 500 Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	47.00%
Russell Mid Cap Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	5.00%
Russell 2000 Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	7.00%
MSCI EAFE Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	5.00%
DJ Global Moderate Index [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	5.00%
MSCI Emerging Market Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	3.00%
BarCap U.S. Govt/Credit [Member]
Defined Benefit Plan Disclosure [Line Items]
Passive portfolio benchmark	28.00%
Genuine Parts Company Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 193,810	191,771
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations	2,055,701	2,187,700
Fair value of plan assets	$ 1,831,513	1,969,196
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	$ 62,335	58,186	$ 56,975
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	$ 4,108	$ 2,600