Line of Credit Facility, Maximum Borrowing Capacity Including Working Capital Facility

No definition available.

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

- Definition

Line of Credit Facility, Remaining Borrowing Capacity Including Working Capital Facilities

+ References

No definition available.

+ Details

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

- Definition

Represents the amount of the subsidiaries' long-term debt that has been guaranteed by the Company.

+ References

No definition available.

+ Details

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

- Definition

Number of Tranches

+ References

No definition available.

+ Details

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

- Definition

Repayment of Debt, Interest

+ References

No definition available.

+ Details

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

- Definition

Repayment of Debt, Principal

+ References

No definition available.

+ Details

Name:	bel_RepaymentofDebtPrincipal
Namespace Prefix:	bel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Annual mandatory amortization (repayment) of secured term loan as a percentage of principal amount.

+ References

No definition available.

+ Details

Name:	bel_Securedtermloanannualmandatoryamortizationpercentageofprincipalamount
Namespace Prefix:	bel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The current and noncurrent portions of long term debt of consolidated VIE.

+ References

No definition available.

+ Details

Name:	bel_VariableInterestEntityCarryingAmountOfLongTermDebtConsolidatedVieIncludingCurrentPortion
Namespace Prefix:	bel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt issuance costs classified as noncurrent. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

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 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Floor rate on an interest rate derivative such as an interest rate floor or collar. If market rates falls below the floor rate, a payment or receipt is triggered on the contract.

+ References

No definition available.

+ Details

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

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12317-112629

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12355-112629

+ Details

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

- Definition

For a debtor, the aggregate gain (loss) recognized on the restructuring of payables arises from the difference between the book value of the debt before the restructuring and the fair value of the payments on the debt after restructuring is complete.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 60
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6402221&loc=d3e15743-112638

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

- 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

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 210.5-02.19(b),22(b))
-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:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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

- Definition

Amount of long-term debt and capital lease obligation 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 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

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

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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

- Details

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Namespace Prefix:
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Balance Type:
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- Details

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Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bel_TrancheOneTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bel_TrancheTwoTermLoanMember
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Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
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- Details

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Debt and obligations under capital lease - Narratives (Details)			1 Months Ended		12 Months Ended
	Jul. 03, 2017 USD ($)	Mar. 21, 2014 USD ($)	Apr. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2017 USD ($) tranche	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2017 EUR (€) tranche	Aug. 31, 2014 USD ($)	Mar. 21, 2014 EUR (€)
Debt Instrument
Long-term debt and obligations under capital leases					$ 700,752,000	$ 585,768,000
Gain on extinguishment of debt					0	1,200,000	$ 0
Guaranteed debt of subsidiaries					611,351,000	488,985,000
Loss on debt restructuring					682,000	0
Deferred financing costs					13,979,000	9,535,000
Line of credit maximum borrowing capacity including working capital facility					100,598,000	105,525,000
Line of credit facility, remaining borrowing capacity including working capital facilities					100,598,000	105,525,000
Variable interest entity, primary beneficiary
Debt Instrument
Long-term debt and obligations under capital leases					112,069,000	111,968,000
Long-term debt, including current portion, held by consolidated variable interest entities					112,857,000	113,098,000
Charleston Center LLC \| Variable interest entity, primary beneficiary
Debt Instrument
Debt instrument, face amount				$ 112,000,000					$ 86,000,000
Repayment of debt, principal				10,000,000
Repayment of debt, interest				$ 16,819,000
Gain on extinguishment of debt						1,200,000
Deferred financing costs					533,000	$ 888,000
Charleston Center LLC \| LIBOR \| Variable interest entity, primary beneficiary
Debt Instrument
Basis spread on variable interest rate, percentage				2.35%
Term facility
Debt Instrument
Debt instrument, term		7 years
Debt instrument, face amount		$ 551,955,000			$ 609,955,000
Proceeds from line of credit			$ 45,000,000
Number of tranches \| tranche					2			2
Interest rate floor					0.00%			0.00%
Secured term loan, annual mandatory amortization, percentage of principal amount					1.00%
Term facility \| Tranche one
Debt Instrument
Debt instrument, face amount		345,000,000
Long-term debt and obligations under capital leases					$ 398,000,000
Term facility \| Tranche one \| LIBOR
Debt Instrument
Basis spread on variable interest rate, percentage					2.75%
Term facility \| Tranche two
Debt Instrument
Debt instrument, face amount		206,955,000								€ 150,000,000
Long-term debt and obligations under capital leases					$ 213,352,000			€ 178,105,000
Term facility \| Tranche two \| EURIBOR
Debt Instrument
Basis spread on variable interest rate, percentage					3.00%
Revolving Credit Facility
Debt Instrument
Debt instrument, term					5 years
Debt instrument, face amount	$ 100,000,000	$ 105,000,000
Line of credit facility, maximum borrowing capacity					$ 100,000,000
Revolving Credit Facility \| LIBOR
Debt Instrument
Basis spread on variable interest rate, percentage					2.50%
Commitment fee, percentage					0.40%
Secured Debt
Debt Instrument
Debt instrument, term	7 years
Debt instrument, face amount	$ 603,434,000