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

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the frequency of periodic payments (monthly, quarterly, annual).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

Reference 2: 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)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentFrequencyOfPeriodicPayment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

+ Details

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

- 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

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

+ Details

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

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3291-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

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

- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: 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))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

- Definition

Debt instrument amendment changes in interest rate terms.

+ References

No definition available.

+ Details

Name:	wstc_DebtInstrumentAmendmentChangesInInterestRateTerms
Namespace Prefix:	wstc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument interest rate stated percentage adjustment.

+ References

No definition available.

+ Details

Name:	wstc_DebtInstrumentInterestRateStatedPercentageAdjustment
Namespace Prefix:	wstc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt instrument interest rate stated percentage rate range minimum adjustment.

+ References

No definition available.

+ Details

Name:	wstc_DebtInstrumentInterestRateStatedPercentageRateRangeMinimumAdjustment
Namespace Prefix:	wstc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument interest rate stated premium percentage rate.

+ References

No definition available.

+ Details

Name:	wstc_DebtInstrumentInterestRateStatedPremiumPercentageRate
Namespace Prefix:	wstc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument optional availability date.

+ References

No definition available.

+ Details

Name:	wstc_DebtInstrumentOptionalAvailabilityDate
Namespace Prefix:	wstc_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instruments optional available tranche or revolving credit facility.

+ References

No definition available.

+ Details

Name:	wstc_DebtInstrumentsOptionalAvailableTrancheOrRevolvingCreditFacility
Namespace Prefix:	wstc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt principal amount amortization rate.

+ References

No definition available.

+ Details

Name:	wstc_DebtPrincipalAmountAmortizationRate
Namespace Prefix:	wstc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Prepayments of long term debt.

+ References

No definition available.

+ Details

Name:	wstc_PrepaymentsOfLongTermDebt
Namespace Prefix:	wstc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Scheduled amortization payments of long term debt.

+ References

No definition available.

+ Details

Name:	wstc_ScheduledAmortizationPaymentsOfLongTermDebt
Namespace Prefix:	wstc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_LoanRestructuringModificationNameAxis=wstc_SeventhAmendmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=wstc_TwoThousandTwentyOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=wstc_SeniorSecuredATermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=wstc_SeniorSecuredBTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=wstc_SeniorSecuredCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationNameAxis=wstc_EighthAmendmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=wstc_TwoThousandTwentyThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=wstc_JuneTwoThousandSixteenToMarchTwoThousandSeventeenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=wstc_MarchTwoThousandSeventeenToMarchTwoThousandEighteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=wstc_MarchTwoThousandEighteenToMarchTwoThousandNineteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=wstc_MarchTwoThousandNineteenToMarchTwoThousandTwentyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=wstc_QuarterlyRateThereafterMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=wstc_TwoThousandTwentyThreeMaturityTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=wstc_TwoThousandTwentyOneMaturityBTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=wstc_TwoThousandNineteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=wstc_TwoThousandEighteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long-Term Obligations - Senior Secured Credit Facilities - Additional Information (Detail) - USD ($)		12 Months Ended
	Jun. 16, 2016	Dec. 31, 2016	Dec. 30, 2016	Dec. 31, 2015
Seventh Amendment [Member]
Debt Instrument [Line Items]
Senior secured credit facility, aggregate principal amount			$ 500,000,000
Debt instrument optional availability date		Jun. 17, 2016
2021 [Member] \| Senior Secured A Term Loan [Member]
Debt Instrument [Line Items]
Secured debt		$ 641,875,000		$ 0
2021 [Member] \| Senior Secured B Term Loan [Member]
Debt Instrument [Line Items]
Secured debt		$ 258,702,000		$ 250,000,000
Senior Secured Credit Facility [Member ]
Debt Instrument [Line Items]
Effective interest rate		4.07%		4.00%
Repayment of long term debt		$ 225,100,000
Scheduled amortization payments		$ 19,800,000
Senior Secured Credit Facility [Member ] \| Senior Secured A Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument frequently periodic payment		quarterly
Senior Secured Credit Facility [Member ] \| 2021 [Member]
Debt Instrument [Line Items]
Debt instrument maturity date	Jul. 01, 2019	Jun. 17, 2021
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured A Term Loan [Member]
Debt Instrument [Line Items]
Secured debt		$ 650,000,000
Effective interest rate		3.02%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured A Term Loan [Member] \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margins		2.25%
Floor rate		0.00%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured A Term Loan [Member] \| Base Rate
Debt Instrument [Line Items]
Interest rate margins		1.25%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured A Term Loan [Member] \| Minimum [Member] \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margins		1.75%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured A Term Loan [Member] \| Minimum [Member] \| Base Rate
Debt Instrument [Line Items]
Interest rate margins		0.75%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured A Term Loan [Member] \| Maximum [Member] \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margins		2.50%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured A Term Loan [Member] \| Maximum [Member] \| Base Rate
Debt Instrument [Line Items]
Interest rate margins		1.50%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured B Term Loan [Member]
Debt Instrument [Line Items]
Secured debt		$ 260,000,000
Debt amortization rate		1.00%
Debt instrument frequently periodic payment		quarterly
Effective interest rate		3.27%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured B Term Loan [Member] \| Eighth Amendment [Member]
Debt Instrument [Line Items]
Premium interest rate		1.00%
Amendment changes in interest rate, description		In addition, the Eighth Amendment provided that, if the effective yield applicable to any incremental term loans issued under the Credit Agreement within 18 months of the Eighth Amendment Effective Date that are “B” term loans ranking equal in priority with respect to the collateral with the 2023 Maturity Term Loans and 2021 Maturity B Term Loans under the Credit Agreement exceeds the effective yield on the “B” term loans outstanding prior to such incremental borrowing by more than 50 basis points (giving effect to original issue discount, if any), then the effective yield on the “B” term loans (other than such incremental term loans) shall be increased by the same amount minus 50 basis points.
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured B Term Loan [Member] \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margins		2.50%
Floor rate		0.00%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured B Term Loan [Member] \| Base Rate
Debt Instrument [Line Items]
Interest rate margins		1.50%
Floor rate		0.00%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured B Term Loan [Member] \| Minimum [Member] \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margins		0.00%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured B Term Loan [Member] \| Minimum [Member] \| Base Rate
Debt Instrument [Line Items]
Interest rate margins		0.00%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured B Term Loan [Member] \| Maximum [Member] \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margins		0.75%
Senior Secured Credit Facility [Member ] \| 2021 [Member] \| Senior Secured B Term Loan [Member] \| Maximum [Member] \| Base Rate
Debt Instrument [Line Items]
Interest rate margins		1.75%
Senior Secured Credit Facility [Member ] \| 2023 [Member]
Debt Instrument [Line Items]
Debt instrument maturity date	Jun. 30, 2018	Jun. 17, 2023
Secured debt		$ 870,000,000
Debt amortization rate		1.00%
Debt instrument frequently periodic payment		quarterly
Effective interest rate		3.27%
Senior Secured Credit Facility [Member ] \| 2023 [Member] \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margins		2.50%
Senior Secured Credit Facility [Member ] \| 2023 [Member] \| Base Rate
Debt Instrument [Line Items]
Interest rate margins		1.50%
Senior Secured Credit Facility [Member ] \| 2023 [Member] \| Minimum [Member] \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margins		0.75%
Senior Secured Credit Facility [Member ] \| 2023 [Member] \| Minimum [Member] \| Base Rate
Debt Instrument [Line Items]
Interest rate margins		1.75%
Senior Secured Credit Facility [Member ] \| June Two Thousand Sixty To March Two Thousand Seventeen \| Senior Secured A Term Loan [Member]
Debt Instrument [Line Items]
Debt amortization rate		2.50%
Senior Secured Credit Facility [Member ] \| March Two Thousand Seventeen To March Two Thousand Eighteen \| Senior Secured A Term Loan [Member]
Debt Instrument [Line Items]
Debt amortization rate		5.00%
Senior Secured Credit Facility [Member ] \| March Two Thousand Eighteen To March Two Thousand Nineteen \| Senior Secured A Term Loan [Member]
Debt Instrument [Line Items]
Debt amortization rate		7.50%
Senior Secured Credit Facility [Member ] \| March Two Thousand Nineteen To March Two Thousand Twenty \| Senior Secured A Term Loan [Member]
Debt Instrument [Line Items]
Debt amortization rate		10.00%
Senior Secured Credit Facility [Member ] \| Quarterly Rate Thereafter [Member] \| Senior Secured A Term Loan [Member]
Debt Instrument [Line Items]
Debt amortization rate		2.50%
Senior Secured Credit Facility [Member ] \| 2023 Maturity Term Loans [Member]
Debt Instrument [Line Items]
Reduction in Basis point range minimum		0.50%
Senior Secured Credit Facility [Member ] \| 2021 Maturity B Term Loans [Member]
Debt Instrument [Line Items]
Reduction in Basis point		0.25%
Senior Secured Credit Facility [Member ] \| 2019 [Member]
Debt Instrument [Line Items]
Prepayment of long term debt		$ 70,000,000
Senior Secured Credit Facility [Member ] \| 2019 [Member] \| Senior Secured A Term Loan [Member]
Debt Instrument [Line Items]
Effective interest rate		2.77%
Senior Secured Credit Facility [Member ] \| 2019 [Member] \| Senior Secured A Term Loan [Member] \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margins		2.00%
Senior Secured Credit Facility [Member ] \| 2019 [Member] \| Senior Secured A Term Loan [Member] \| Base Rate
Debt Instrument [Line Items]
Interest rate margins		1.00%
Senior Secured Credit Facility [Member ] \| 2019 [Member] \| Senior Secured A Term Loan [Member] \| Minimum [Member] \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margins		1.50%
Senior Secured Credit Facility [Member ] \| 2019 [Member] \| Senior Secured A Term Loan [Member] \| Minimum [Member] \| Base Rate
Debt Instrument [Line Items]
Interest rate margins		0.50%
Senior Secured Credit Facility [Member ] \| 2019 [Member] \| Senior Secured A Term Loan [Member] \| Maximum [Member] \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margins		2.25%
Senior Secured Credit Facility [Member ] \| 2019 [Member] \| Senior Secured A Term Loan [Member] \| Maximum [Member] \| Base Rate
Debt Instrument [Line Items]
Interest rate margins		1.25%
Senior Secured Credit Facility [Member ] \| 2018 [Member]
Debt Instrument [Line Items]
Repayment of long term debt		$ 25,900,000
Prepayment of long term debt		$ 109,400,000