Debt - Additional Information (Detail)	1 Months Ended					12 Months Ended
	Feb. 24, 2017 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Apr. 30, 2013 USD ($)	Apr. 30, 2012 USD ($)	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	May 31, 2012 USD ($)
Debt Instrument [Line Items]
Notes issued, aggregate principal amount						$ 239,097,000	$ 323,548,000
Interest expense						15,663,000	19,548,000	$ 22,165,000
Line of credit facility, decrease, repayments						618,000	1,134,000	806,000
Gains (losses) on extinguishment of debt, total						(1,895,000)	(5,808,000)	(1,042,000)
Shareholders' Equity
Debt Instrument [Line Items]
Debt instrument, repurchase amount						82,000,000	19,000,000
Debt instrument, repurchased face amount						98,900,000
Business combination, recognized identifiable assets acquired and liabilities assumed, current liabilities, long-term debt							22,900,000
Gains (losses) on extinguishment of debt, total						$ 1,900,000	200,000
Convertible Senior Notes
Debt Instrument [Line Items]
Notes issued, aggregate principal amount					$ 150,000,000
Notes issued, interest rate					3.375%
Notes issued, interest payment frequency						semi-annually
Convertible Senior Notes | Walker Group Holdings LLC
Debt Instrument [Line Items]
Proceeds from issuance of convertible senior notes						$ 145,100,000
Debt Instrument Maturity Year					2018
Unsecured Debt | Convertible Senior Notes
Debt Instrument [Line Items]
Notes issued, aggregate principal amount						$ 150,000,000
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
Notes initial conversion price | $ / shares						$ 11.70
Convertible notes, conversation date						Nov. 01, 2017
Proceeds from notes issued						$ 1,000
Estimated implied interest rate						7.00%
Fair value of liability component upon issuance						$ 123,800,000
Difference between cash proceeds before offering expenses and the estimated fair value of liability component						21,700,000
Proceeds from issuance of convertible senior notes						145,500,000
Debt Conversion, Converted Instrument, Amount						$ 17,000,000
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						$ 8,300,000	8,500,000	10,000,000
Long-term debt						1,900,000	1,400,000	42,100,000
Interest expense						200,000	300,000	$ 1,100,000
Revolving Credit Facility
Debt Instrument [Line Items]
Notes issued, aggregate principal amount		$ 150,000,000
Credit facility, borrowing capacity		$ 175,000,000
Credit facility, interest rate above basis		12.50%
Line of Credit Facility, Remaining Borrowing Capacity						$ 333,000,000
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 Date, Description						extends the maturity date of the Credit Facility from May 2017 to June 2020
Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Debt Instrument, Description of Variable Rate Basis						basis points to 200 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
Revolving Credit Facility | Senior Secured Credit Facility
Debt Instrument [Line Items]
Notes issued, aggregate principal amount		$ 175,000,000				$ 75,000,000
Debt Instrument, Term						5 years
Term Loan Credit Facility
Debt Instrument [Line Items]
Notes issued, aggregate principal amount						$ 189,470,000	$ 191,399,000
Line of credit facility potential term extension period			91 days
Term Loan Credit Facility | LIBOR
Debt Instrument [Line Items]
Debt Instrument, Maturity Date, Description	LIBOR (subject to a floor of 0%) plus a margin of 2.75% or (ii) a base rate (subject to a floor of 0%) plus a margin of 1.75%.
Term Loan Credit Facility | Incremental Senior Credit Facility
Debt Instrument [Line Items]
Senior Secured Leverage Ratio						3.0 to 1.0
Term Loan Credit Facility | 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
Term Loan Credit Facility | Tranche B One Loan [Member]
Debt Instrument [Line Items]
Notes issued, aggregate principal amount			$ 192,800,000
Term Loan Credit Facility | Tranche B Two Loan [Member]
Debt Instrument [Line Items]
Notes issued, aggregate principal amount			$ 192,800,000
Term Loan Credit Agreement
Debt Instrument [Line Items]
Percentage of tranche loan amount on equal quarterly installments	0.25%		0.25%
Line of Credit Facility, Amount Outstanding						$ 189,500,000
Debt Instrument, Periodic Payment, Principal						$ 1,900,000
Term Loan Credit Agreement | Senior Secured Credit Facility
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding									$ 300,000,000
Term Loan Credit Agreement | Tranche B Two Loan [Member]
Debt Instrument [Line Items]
Notes issued, aggregate principal amount	$ 189,500,000
Minimum
Debt Instrument [Line Items]
Debt Conversion, Converted Instrument, Amount			$ 125,000,000
Minimum | Unsecured Debt | Convertible Senior Notes | Scenario 1
Debt Instrument [Line Items]
Number of trading days						20 days
Minimum | Revolving Credit Facility | Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Fixed Charge Coverage Ratio Minimum		1.0
Maximum | Revolving Credit Facility | Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Fixed Charge Coverage Ratio Minimum		1.1