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Supplemental Disclosures of Cash Flow Information - Additional Information (Detail) - Qualified Contributory Savings and Thrift 401(k) Plan [Member] - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2021	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Matching contributions by employer, percentage		100.00%
Percentage of eligible compensation for matching contributions by employer	5.00%	5.00%
Matching contributions vesting schedule		5 years
Contribution expense to plan		$ 51.8	$ 45.9

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- Definition

Defined benefit plan percentage of eligible compensation for matching contributions by employer.

+ References

No definition available.

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X

- Definition

Matching contributions vesting schedule.

+ 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 cost for defined contribution plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-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.

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- Details

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