Employee Benefit Plans - Fair Value of Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	$ 2,756,803	$ 2,545,359	$ 2,311,227
Assets Measured at NAV	64,669	204,303
Common stocks — mutual funds — equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	388,591	586,196
Assets Measured at NAV	64,669	204,303
Genuine Parts Company common stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	210,510	202,711
Assets Measured at NAV	0	0
Other stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	971,020	989,258
Assets Measured at NAV	0	0
Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	46,815	30,746
Assets Measured at NAV	0	0
Cash and equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	22,084	18,631
Assets Measured at NAV	0	0
Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	425,877	257,221
Assets Measured at NAV	0	0
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	598,216	393,450
Assets Measured at NAV	0	0
Asset-backed and mortgage-backed securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	12,894	10,161
Assets Measured at NAV	0	0
Other-international
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	61,008	39,992
Assets Measured at NAV	0	0
Municipal bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	19,621	14,724
Assets Measured at NAV	0	0
Options and Futures
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	167
Assets Measured at NAV	0
Cash surrender value of life insurance policies
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets		2,269
Assets Measured at NAV		0
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	1,971,357	1,852,568
Quoted Prices in Active Markets for Identical Assets (Level 1) | Common stocks — mutual funds — equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	323,922	381,893
Quoted Prices in Active Markets for Identical Assets (Level 1) | Genuine Parts Company common stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	210,510	202,711
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	971,020	989,258
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	46,815	30,746
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	22,084	18,631
Quoted Prices in Active Markets for Identical Assets (Level 1) | Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	350,706	192,288
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Asset-backed and mortgage-backed securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other-international
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	46,133	37,041
Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Options and Futures
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	167
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash surrender value of life insurance policies
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets		0
Significant Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	720,777	486,219
Significant Observable Inputs (Level 2) | Common stocks — mutual funds — equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Observable Inputs (Level 2) | Genuine Parts Company common stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Observable Inputs (Level 2) | Other stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Observable Inputs (Level 2) | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Observable Inputs (Level 2) | Cash and equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Observable Inputs (Level 2) | Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	75,171	64,933
Significant Observable Inputs (Level 2) | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	598,216	393,450
Significant Observable Inputs (Level 2) | Asset-backed and mortgage-backed securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	12,894	10,161
Significant Observable Inputs (Level 2) | Other-international
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	14,875	2,951
Significant Observable Inputs (Level 2) | Municipal bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	19,621	14,724
Significant Observable Inputs (Level 2) | Options and Futures
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0
Significant Observable Inputs (Level 2) | Cash surrender value of life insurance policies
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets		0
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	2,269
Significant Unobservable Inputs (Level 3) | Common stocks — mutual funds — equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Unobservable Inputs (Level 3) | Genuine Parts Company common stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Unobservable Inputs (Level 3) | Other stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Unobservable Inputs (Level 3) | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Unobservable Inputs (Level 3) | Cash and equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Unobservable Inputs (Level 3) | Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Unobservable Inputs (Level 3) | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Unobservable Inputs (Level 3) | Asset-backed and mortgage-backed securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Unobservable Inputs (Level 3) | Other-international
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Unobservable Inputs (Level 3) | Municipal bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	0	0
Significant Unobservable Inputs (Level 3) | Options and Futures
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets	$ 0
Significant Unobservable Inputs (Level 3) | Cash surrender value of life insurance policies
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets		$ 2,269