Employee Benefits - Defined Contribution Plan (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Deferred compensation plan
Number of investments, which are taken as reference to measure the interest that may be acquired \| item	3
Employer contribution as percentage of the employees' reduced compensation	3.00%
Number of deferred compensation plans \| item	2
Deferred compensation plan expense	$ (11)	$ 2	$ (10)
Deferred compensation plan liability included in other liabilities	45	38
Deferred compensation plan assets included in other current assets	51	45
Investment income related to the mark-to-market of investments treated as trading securities	$ 11	$ (2)	$ 9
United States
Defined contribution plans
Employer contribution (as a percent of employee contributions)	50.00%	50.00%	50.00%
Employer contribution limit per calendar year (as a percent of compensation)	6.00%	6.00%	6.00%
Vesting percentage after one year of service	20.00%	20.00%	20.00%
Additional vesting percentage with each additional complete year of service	20.00%	20.00%	20.00%
Contribution expense	$ 3	$ 3	$ 3
Defined contribution plan covering hourly, non-union employees
Defined contribution plans
Contribution expense		$ 1	$ 1
Defined contribution plan covering hourly, non-union employees \| Maximum
Defined contribution plans
Contribution expense	$ 1

The compensation expense recognized during the period relating to the deferred compensation arrangement.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the employer's contribution as a percentage of employees' reduced compensation under the deferred compensation plan which allows certain employees to reduce their compensation in exchange for values in investments.

+ References

No definition available.

+ Details

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- Definition

Represents the number of investments, which are taken as reference to measure the interest that may be acquired by employees in exchange for reduction in their compensation.

+ References

No definition available.

+ Details

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- References

No definition available.

+ Details

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- Definition

Represents the deferred compensation plan investment income (loss) related to the mark-to-market of the investments treated as trading securities.

+ References

No definition available.

+ Details

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Namespace Prefix:	seb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the percentage of vesting after first year of service.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the additional vesting percentage with each additional completed year of service, after the first year of service.

+ References

No definition available.

+ Details

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Namespace Prefix:	seb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of deferred compensation plans.

+ References

No definition available.

+ Details

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- Definition

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements payable beyond one year (or the operating cycle, if longer).

+ References

No definition available.

+ Details

Name:	us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of assets held under deferred compensation agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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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Data Type:	xbrli:stringItemType
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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.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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- Details

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