Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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(a)(1))

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

+ Details

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

- Details

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

- Definition

Amount of debt issuance costs (for example, but not limited to, legal, accounting, broker, and regulatory fees).

+ References

No definition available.

+ Details

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

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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

- Definition

The cash outflow for the settlement of obligation drawn from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the 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=31042434&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

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

- Definition

The cash outflow for the payment of other borrowing not otherwise defined in the taxonomy.

+ References

+ Details

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

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ 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 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16(a))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

+ Details

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

Debt - Cabot Senior Secured Notes (Detail)	3 Months Ended			3 Months Ended						3 Months Ended		0 Months Ended
Debt - Cabot Senior Secured Notes (Detail)	Mar. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2014 USD ($)	Mar. 31, 2015 Cabot Corporation [Member] USD ($)	Mar. 31, 2015 Cabot Corporation [Member] GBP (£)	Sep. 20, 2012 Cabot 2019 Notes [Member] USD ($)	Sep. 20, 2012 Cabot 2019 Notes [Member] GBP (£)	Aug. 02, 2013 Cabot 2020 Notes [Member] USD ($)	Aug. 02, 2013 Cabot 2020 Notes [Member] GBP (£)	Mar. 31, 2015 J Bridge PECs [Member] USD ($)	Mar. 31, 2015 J Bridge PECs [Member] GBP (£)	Mar. 27, 2014 Cabot 2021 Notes [Member] USD ($)	Mar. 27, 2014 Cabot 2021 Notes [Member] GBP (£)	Mar. 27, 2014 Cabot 2021 Notes [Member] USD ($)	Mar. 27, 2014 Cabot 2021 Notes [Member] GBP (£)	Jul. 25, 2013 Senior Secured Notes Due 2020 [Member] Marlin Acquisition [Member] USD ($)	Jul. 25, 2013 Senior Secured Notes Due 2020 [Member] Marlin Acquisition [Member] GBP (£)
Debt Instrument [Line Items]
Encore senior secured notes	$ 40,000,000us-gaap_SeniorNotes		$ 43,750,000us-gaap_SeniorNotes			$ 438,400,000	£ 265,000,000	$ 151,700,000	£ 100,000,000					$ 291,800,000	£ 175,000,000.0	$ 246,500,000	£ 150,000,000.0
Debt instrument, stated interest rate (percent)						10.375%	10.375%	8.375%	8.375%					6.50%	6.50%	10.50%	10.50%
Repayment of senior credit facility	124,395,000	447,045,000		113,800,000	75,000,000							174,800,000	105,000,000
Repayment of J Bridge PECs										37,900,000	25,000,000.0
Debt issuance cost												7,500,000
Long-term debt, fair value																$ 284,200,000