Notes Payable - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Collateral Account used for future payments	$ 2.4	$ 0.1	$ 25.0
Principal and interest payments	2.4us-gaap_DebtInstrumentPeriodicPayment	0.1us-gaap_DebtInstrumentPeriodicPayment	25.0us-gaap_DebtInstrumentPeriodicPayment
13% Senior First Lien Notes [Member]
Debt Instrument [Line Items]
Issued aggregate principal amount	110.0
Notes maturity date	Mar. 19, 2030
Principal payments	78.9	36.3	2.1
Cash interest paid on Notes	5.2	9.7	3.7
13% Senior Second Lien Notes [Member]
Debt Instrument [Line Items]
Issued aggregate principal amount	20.0
Notes maturity date	Mar. 19, 2030
PIK Notes [Member]
Debt Instrument [Line Items]
Issued aggregate principal amount	18.5	13.9	8.3
Runoff Notes [Member]
Debt Instrument [Line Items]
Outstanding amounts of notes	$ 31.2	$ 105.5	$ 136.3

Carrying amount as of the balance sheet date of cash collateral held for borrowed securities, for which the cash is restricted as to withdrawal or usage.

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 210.9-03.1)

-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

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-Section S99

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-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 2

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- 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 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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- Details

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- Definition

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

+ References

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

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-Name Accounting Standards Codification

-Topic 210

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-Section S99

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- Definition

Amount of the required periodic payments including both interest and principal payments.

+ References

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

-Publisher FASB

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-Topic 210

-SubTopic 10

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

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- Definition

Aggregate amount of interest paid or due on all long-term debt.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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- Definition

Notes payable outstanding.

+ References

No definition available.

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- Definition

Redemption amount of principal.

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