Debt - Additional Information (Detail) - Debt Instrument, Name [Domain]		1 Months Ended				3 Months Ended		6 Months Ended
	Jun. 04, 2015 USD ($)	Mar. 19, 2015 USD ($)	Apr. 30, 2013 USD ($)	Nov. 30, 2012 USD ($)	Apr. 30, 2012 USD ($)	Jun. 30, 2015 USD ($) $ / shares	Jun. 30, 2014 USD ($) $ / shares	Jun. 30, 2015 USD ($) $ / shares	Jun. 30, 2014 USD ($) $ / shares	Dec. 31, 2014 USD ($)	May. 31, 2012 USD ($)
Debt Instrument [Line Items]
Notes issued, aggregate principal amount						$ 343,762,000		$ 343,762,000		$ 344,490,000
Notes initial conversion price | $ / shares						$ 11.70	$ 11.70	$ 11.70	$ 11.70
Current portion of long-term debt						$ 5,513,000		$ 5,513,000		496,000
Debt issuance costs paid								2,467,000	$ 0
Interest expense						4,802,000	$ 5,733,000	9,975,000	11,450,000
Line of credit facility, decrease, repayments								416,000	366,000
Proceeds from Sale of Property, Plant, and Equipment								13,168,000	$ 81,000
Loan Agreement
Debt Instrument [Line Items]
Notes issued, aggregate principal amount				$ 2,500,000
Notes issued, interest rate				4.25%
Long-term debt						1,400,000		1,400,000
Current portion of long-term debt						500,000		500,000
Debt Instrument, Maturity Date, Description				matures in March 2018
Convertible Senior Notes
Debt Instrument [Line Items]
Notes issued, aggregate principal amount					$ 150,000,000
Notes issued, interest rate					3.375%
Debt Instrument Maturity Year					2018
Convertible Senior Notes | Walker Group Holdings Llc [Member]
Debt Instrument [Line Items]
Proceeds from issuance of convertible senior notes								$ 145,100,000
Unsecured Debt | Convertible Senior Notes
Debt Instrument [Line Items]
Notes initial conversion rate per 1,000 in principal amount								85.4372
Principal amount of notes conversation for 85.4372 shares of common stock						$ 1,000		$ 1,000
Notes initial conversion price | $ / shares						$ 11.70		$ 11.70
Convertible notes, conversation date								Nov. 01, 2017
Proceeds from notes issued								$ 1,000
Estimated implied interest rate						7.00%		7.00%
Fair value of liability component upon issuance						$ 123,800,000		$ 123,800,000
Difference between cash proceeds before offering expenses and the estimated fair value of liability component						21,700,000		21,700,000
Proceeds from issuance of convertible senior notes								145,500,000
Debt Conversion, Converted Instrument, Amount								$ 11,000,000
Unsecured Debt | Convertible Senior Notes | Scenario 1
Debt Instrument [Line Items]
Number of consecutive trading days									30 days
Last reported sale price of common stock as percentage of conversion price								130.00%
Unsecured Debt | Convertible Senior Notes | Scenario 2
Debt Instrument [Line Items]
Convertible senior notes, trading price per $1,000 principal amount of notes as percentage of the product of the last reported sale price of common stock and the conversion rate								98.00%
Amended Credit Agreement
Debt Instrument [Line Items]
Interest Paid								$ 4,300,000	$ 5,400,000
Current portion of long-term debt						5,000,000		5,000,000
Debt issuance costs paid								900,000
Interest expense								200,000	500,000
Other Expenses								5,300,000
Debt Instrument, Periodic Payment, Principal								500,000	$ 21,400,000
Revolving Credit Facility
Debt Instrument [Line Items]
Notes issued, aggregate principal amount	$ 150,000,000
Credit facility, borrowing capacity	$ 175,000,000
Line of Credit Facility, Remaining Borrowing Capacity						308,300,000		308,300,000
Debt Instrument, Term	5 years
Line Of Credit Facility Amendment Description	Liquidity of at least $125 million and (y) availability under the Credit Facility of at least $25 million. Liquidity, as defined in the Credit Agreement, reflects the difference between (i) the sum of (A) unrestricted cash and cash equivalents and (B) availability under the Credit Facility and (ii) the amount necessary to fully redeem the Notes.
Debt Instrument Maturity Term Description	extends the maturity date of the Credit Facility from May 8, 2017 to June 4, 2020
Proceeds from Sale of Property, Plant, and Equipment								$ 13,100,000
Debt Instrument Payment Description								Further, a mandatory principal payment is required for asset sales greater than $10.0 million, with the amount of the required payment equal to the excess above $10.0 million, or $3.1 million.
Revolving Credit Facility | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt Instrument, Description of Variable Rate Basis	basis points (in lieu of the previous range from 175 basis points to 225 basis points), or (y) a base rate plus a margin ranging from 50 basis points to 100 basis points (in lieu of the previous range from 75 basis points to 125 basis points), in each case, based upon the monthly average excess availability under the Credit Facility, (ii) provides that the monthly unused line fee shall be equal to 25 basis points (which amount was previously 37.5 basis points) times the average unused availability under the Credit Facility, (iii) provides that if availability under the Credit Facility is less than 12.5% (which threshold was previously 15%) of the total commitment under the Credit Facility or if there exists an event of default, amounts in any of the Borrowers and the subsidiary guarantors deposit accounts (other than certain excluded accounts) will be transferred daily into a blocked account held by the Agent and applied to reduce the outstanding amounts under the Credit Facility
Debt Instrument Fixed Coverage Ratio Description	provides that the Company will be required to maintain a minimum fixed charge coverage ratio of not less than 1.1 to 1.0 as of the end of any period of 12 fiscal months when excess availability under the Credit Facility is less than 10% (which threshold was previously 12.5%) of the total commitment under the Credit Facility
Revolving Credit Facility | Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Credit facility, maturity date								May 08, 2017
Term Loan Credit Facilty
Debt Instrument [Line Items]
Notes issued, aggregate principal amount						$ 192,363,000		$ 192,363,000		$ 192,845,000
Credit facility, maturity date		Mar. 19, 2022
Line of credit facility potential term extension period		91 days
Percentage of tranche loan amount on equal quarterly installments		0.25%
Debt Instrument Payment Percentage		1.00%
Term Loan Credit Facilty | LIBOR
Debt Instrument [Line Items]
Debt Instrument, Maturity Date, Description		(i) LIBOR (subject to a floor of 1.00%) plus a margin of 3.25% or (ii) a base rate plus a margin of 2.25%.
Term Loan Credit Facilty | Senior Secured Credit Facility
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding											$ 300,000,000
Term Loan Credit Facilty | Incremental Senior Credit Facility
Debt Instrument [Line Items]
Credit facility, borrowing capacity			$ 75,000,000
Senior Secured Leverage Ratio			3.00 to 1.00
Term Loan Credit Facilty | Amended Credit Agreement
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity			$ 297,000,000
Long-term debt			277,000,000
Line of credit facility, decrease, repayments			$ 20,000,000
Minimum
Debt Instrument [Line Items]
Debt Conversion, Converted Instrument, Amount		$ 125,000,000