Employee Benefit Plans - Additional Information (Detail) - USD ($) shares in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Discretionary profit sharing	$ 0	$ 0	$ 0
Contribution plan, employer matching contribution percentage		50.00%	50.00%
Defined contribution plans employee contribution percentage of eligible compensation matched by employer		6.00%	6.00%
Shares allocated to the employee stock ownership plan	0.7	0.7
Contribution expense under employee stock ownership plan	$ 8,600,000	$ 4,700,000	$ 5,000,000.0
Employer Matching Contribution Tranche One [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution plan, employer matching contribution percentage	75.00%
Defined contribution plans employee contribution percentage of eligible compensation matched by employer	4.00%
Employer Matching Contribution Tranche Two [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution plan, employer matching contribution percentage	50.00%
Defined contribution plans employee contribution percentage of eligible compensation matched by employer	4.00%
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 0
Discretionary profit sharing			7,600,000
Settlement loss			9,800,000
Benefit cost, net periodic benefit cost			$ 11,600,000

Defined contribution plans employee contribution percentage of eligible compensation matched by employer.

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- Definition

The number of company shares in the 401(k) plan. Company shares owned through the 401(k) plan are included in the calculation of weighted-average shares outstanding for purposes of calculating basic and diluted earnings-per-share.

+ References

No definition available.

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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 net periodic benefit cost (credit) for defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
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- Definition

Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement.

+ References

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

Amount of payment, which decreases plan assets of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract.

+ References

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- Definition

Amount of cost for defined contribution plan.

+ References

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- Definition

Amount of discretionary contributions made by an employer to a defined contribution plan.

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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