The amount of variable-rate long-term debt covered by interest which convert the interest rate to a fixed rate.

No definition available.

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Namespace Prefix:	swm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Bank Overdraft Facilities

+ References

No definition available.

+ Details

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Balance Type:	credit
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- Definition

Debt Instrument, Covenant, EBITDA Ratio

+ References

No definition available.

+ Details

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- Definition

Debt Instrument, Covenant, Interest Rate Coverage

+ References

No definition available.

+ Details

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- Definition

Quarterly Debt Amortization Rate - A-1 - Final 3 Years

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Debt Amortization Rate - Quarterly Repayment Rate of Debt Principal

+ References

No definition available.

+ Details

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- Definition

Quarterly Debt Amortization Rate - A-2

+ References

No definition available.

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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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
Balance Type:	na
Period Type:	duration

- Definition

The effective interest rate at the end of the reporting period.

+ References

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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- Details

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- Details

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Debt (Details)	1 Months Ended	12 Months Ended
Debt (Details)	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)	Oct. 01, 2016	Oct. 28, 2015 USD ($)
Debt Instrument [Line Items]
Debt amortization rate on A1 for first two years				5.00%
Debt amortization rate on A1 for final three years				10.00%
Debt amortization rate on A2				1.00%
Amount of long term debt covered by interest rate swaps		$ 50,000,000
French Employee Profit Sharing [Member]
Debt Instrument [Line Items]
Interest rate at period end	1.08%	0.80%
Bank Overdrafts [Member]
Debt Instrument [Line Items]
Interest rate at period end	0.30%	0.14%
Bank overdraft facilities	$ 28,900,000	$ 27,300,000
Second Amended and Restated Credit Agreement [Member]
Debt Instrument [Line Items]
Maximum borrowings under credit facility				$ 1,000,000,000
Second Amended and Restated Credit Agreement [Member] \| Maximum [Member]
Debt Instrument [Line Items]
EBITDA ratio			3.00	3.50
Second Amended and Restated Credit Agreement [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Interest rate coverage				3.00
Term Loan A-1 [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 100,000,000
Prepayment of amortization for term loan	$ 40,000,000
Line of Credit Facility, Interest Rate at Period End		2.50%
Term Loan A-2 [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				250,000,000
Line of Credit Facility, Interest Rate at Period End		2.81%
Revolving Credit Facility [Member] \| Second Amended and Restated Credit Agreement [Member]
Debt Instrument [Line Items]
Maximum borrowings under credit facility				$ 650,000,000
Revolving Credit Facility [Member] \| Revolving Credit Agreement - euro borrowings [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End		1.75%
Revolving Credit Facility [Member] \| Revolving Credit Agreement - U.S. dollar borrowings [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End		2.53%
Base Rate [Member] \| Term Loan A-1 [Member] \| Term Loan [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.25%
Base Rate [Member] \| Term Loan A-1 [Member] \| Term Loan [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.25%
Base Rate [Member] \| Term Loan A-2 [Member] \| Term Loan [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.50%
Base Rate [Member] \| Term Loan A-2 [Member] \| Term Loan [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.50%
Base Rate [Member] \| Revolving Credit Facility [Member] \| Second Amended and Restated Credit Agreement [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.25%
Base Rate [Member] \| Revolving Credit Facility [Member] \| Second Amended and Restated Credit Agreement [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.25%
London Interbank Offered Rate (LIBOR) [Member] \| Term Loan A-1 [Member] \| Term Loan [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.25%
London Interbank Offered Rate (LIBOR) [Member] \| Term Loan A-1 [Member] \| Term Loan [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.25%
London Interbank Offered Rate (LIBOR) [Member] \| Term Loan A-2 [Member] \| Term Loan [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.50%
London Interbank Offered Rate (LIBOR) [Member] \| Term Loan A-2 [Member] \| Term Loan [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.50%
London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member] \| Second Amended and Restated Credit Agreement [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.25%
London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member] \| Second Amended and Restated Credit Agreement [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.25%