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

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.

+ Details

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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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(8)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

+ Details

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- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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Employee Benefit Plans - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
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				6.00%
Contribution expense under employee stock ownership plan	$ 1,900,000	$ 1,100,000			$ 6,500,000	$ 3,500,000
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