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Employee Benefits - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Qualified employees maximum contribution to defined contribution savings plan allowed in percentage of annual compensation	75.00%
Company contribution, percentage company contribution matches of the employee's percentage contribution matched	100.00%
Employee retirement savings plan matching expenses	$ 213.0	$ 192.0	$ 179.0
Vesting service period for defined benefit pension plan	3 years
Global Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	30.00%
Domestic Mid-Small Cap Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	5.00%
Emerging Markets Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	5.00%
Real Estate Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	10.00%
Long-duration bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	35.00%
Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	5.00%
Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset allocation for the company's qualified pension plan	10.00%
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions to qualified pension and postretirement welfare plan	$ 26.0	1,153.0
Plan assets measured at fair value	8,113.0	7,498.0	5,838.0
Pension Plans [Member] \| Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions to qualified pension and postretirement welfare plan	0.0	1,100.0
Company contributions to pension and postretirement welfare plan in next fiscal year	0.0	1,100.0
Pension Plans [Member] \| Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions to pension and postretirement welfare plan in next fiscal year	26.0
Pension Plans [Member] \| Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	450.0	251.0
Pension Plans [Member] \| Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	814.0	419.0
Postretirement Welfare Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions to qualified pension and postretirement welfare plan	3.0	5.0
Company contributions to pension and postretirement welfare plan in next fiscal year	4.0
Plan assets measured at fair value			$ 84.0
Management Arrangement With Related Party [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	$ 55.3	$ 1,000.0