Multiplier Applied to PSU Awards at Settlement Sub Event

No definition available.

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- Definition

The multiplier applied to the PSU awards at settlement to determine the number of shares of the Company’s common stock to be issued at the completion of the performance period.

+ References

No definition available.

+ Details

Name:	sm_MultiplierAppliedToPsuAwardsAtSettlement
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Balance Type:	na
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- Definition

Number of Shares Represented by Each RSU

+ References

No definition available.

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

RestrictedStockSharesSettledGrossofSharesforTaxWithholdings

+ References

No definition available.

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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

- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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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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Data Type:	xbrli:stringItemType
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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of shares issued under share-based payment arrangement.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares used to settle grantee's tax withholding obligation for award under share-based payment arrangement.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number, before forfeiture, of shares issued under share-based payment arrangement. Excludes employee stock ownership plan (ESOP).

+ References

No definition available.

+ Details

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Data Type:	xbrli:sharesItemType
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- Details

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- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
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Compensation Plans: Stock Based (Details) $ in Millions			3 Months Ended		6 Months Ended
Compensation Plans: Stock Based (Details) $ in Millions	Jul. 01, 2020 shares	Jun. 30, 2020 USD ($) shares	Jun. 30, 2020 USD ($) shares	Jun. 30, 2019 USD ($) shares	Jun. 30, 2020 USD ($) shares	Jun. 30, 2019 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant		4,200,000	4,200,000		4,200,000
Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued to directors			267,576	96,719
Performance Shares (PSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period (on non-printing section)		3 years
Stock-based compensation expense \| $			$ 2.8	$ 2.9	$ 5.4	$ 5.7
Unrecognized stock based compensation expense \| $		$ 10.0	$ 10.0		$ 10.0
Performance Shares (PSUs) \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Issued in Period	485,060
Shares Withheld for Tax Withholding Obligation	215,451
Multiplier Applied to PSU Awards at Settlement Sub Event	0.9
Performance Shares (PSUs) \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier applied to PSU awards at settlement		0	0		0
Performance Shares (PSUs) \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier applied to PSU awards at settlement		2	2		2
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period (on non-printing section)		3 years
Stock-based compensation expense \| $			$ 2.7	$ 2.8	$ 5.3	$ 5.5
Unrecognized stock based compensation expense \| $		$ 10.8	$ 10.8		$ 10.8
Number of shares represented by each RSU		1	1		1
Restricted Stock Units (RSUs) \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs settled, awards granted in previous years	587,088
Shares Issued in Period	420,562
Shares Withheld for Tax Withholding Obligation	166,526