Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 8

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Debt - Additional Information (Detail) (USD $)	1 Months Ended			12 Months Ended					1 Months Ended				12 Months Ended		12 Months Ended		1 Months Ended			12 Months Ended					12 Months Ended							1 Months Ended	12 Months Ended	1 Months Ended				12 Months Ended			1 Months Ended	12 Months Ended		1 Months Ended				12 Months Ended
Debt - Additional Information (Detail) (USD $)	Jun. 30, 2011	May 31, 2011	Jul. 31, 2009	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jun. 30, 2012	Aug. 31, 2011	Nov. 27, 2012 Industrial Revenue Bond	Dec. 31, 2012 Industrial Revenue Bond	Dec. 31, 2011 Industrial Revenue Bond	Dec. 31, 2012 Convertible Senior Notes	Dec. 31, 2012 Unsecured Debt Convertible Senior Notes	Apr. 23, 2012 Unsecured Debt Convertible Senior Notes	Dec. 31, 2012 Unsecured Debt Convertible Senior Notes Scenario 1	Dec. 31, 2012 Unsecured Debt Convertible Senior Notes Scenario 2	May 08, 2012 Revolving Credit Facility	Aug. 31, 2011 Revolving Credit Facility Amended and Restated Credit Agreement	May 31, 2010 Revolving Credit Facility Amended and Restated Credit Agreement	Dec. 31, 2012 Revolving Credit Facility Amended and Restated Credit Agreement	Dec. 31, 2011 Revolving Credit Facility Amended and Restated Credit Agreement	Jul. 31, 2011 Revolving Credit Facility Amended and Restated Credit Agreement	Dec. 31, 2012 Revolving Credit Facility Amended and Restated Credit Agreement Option to increase subject to certain conditions	Dec. 31, 2012 Revolving Credit Facility Amended and Restated Credit Agreement Swing Line Loan	Dec. 31, 2012 Term Loan Credit Facilty	Dec. 31, 2012 Term Loan Credit Facilty LIBOR	Dec. 31, 2012 Term Loan Credit Facilty Base Rate	May 08, 2012 Term Loan Credit Facilty Senior Secured Credit Facility	May 08, 2012 Term Loan Credit Facilty Incremental Senior Credit Facility	Dec. 31, 2012 Letter of Credit Revolving Credit Facility Amended and Restated Credit Agreement	Dec. 31, 2012 Letter Of Credit Subfacility Revolving Credit Facility Amended and Restated Credit Agreement	Aug. 31, 2011 Minimum	Dec. 31, 2012 Minimum Unsecured Debt Convertible Senior Notes Scenario 1	Aug. 31, 2011 Minimum Revolving Credit Facility Amended and Restated Credit Agreement	Dec. 31, 2012 Minimum Revolving Credit Facility Amended and Restated Credit Agreement	Dec. 31, 2012 Minimum Revolving Credit Facility Amended and Restated Credit Agreement LIBOR	Dec. 31, 2012 Minimum Revolving Credit Facility Amended and Restated Credit Agreement Base Rate	Dec. 31, 2012 Minimum Term Loan Credit Facilty Through September 30, 2013	Dec. 31, 2012 Minimum Term Loan Credit Facilty Thereafter through September 30, 2015	Dec. 31, 2012 Minimum Term Loan Credit Facilty Thereafter	Aug. 31, 2011 Maximum	Dec. 31, 2012 Maximum	Dec. 31, 2012 Maximum Swing Line Loan	Aug. 31, 2011 Maximum Revolving Credit Facility Amended and Restated Credit Agreement	Dec. 31, 2012 Maximum Revolving Credit Facility Amended and Restated Credit Agreement	Dec. 31, 2012 Maximum Revolving Credit Facility Amended and Restated Credit Agreement LIBOR	Dec. 31, 2012 Maximum Revolving Credit Facility Amended and Restated Credit Agreement Base Rate	Dec. 31, 2012 Maximum Term Loan Credit Facilty Through September 30, 2013	Dec. 31, 2012 Maximum Term Loan Credit Facilty Thereafter through September 30, 2015	Dec. 31, 2012 Maximum Term Loan Credit Facilty Thereafter	Dec. 31, 2012 Maximum Letter of Credit
Notes issued, due date														2018
Notes issued, aggregate principal amount										$ 2,500,000	$ 0	$ 150,000,000		$ 150,000,000
Notes issued, interest rate									4.25%					3.375%
Notes issued, interest payment frequency													Semi-annually
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												$ 11.70	$ 11.70
Convertible notes, conversation date													Nov. 01, 2017
Number of trading days															30 days																		20 days
Number of consecutive trading days															30 days	5 days
Last reported sale price of common stock as percentage of conversion price																																	130.00%
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%
Proceeds from notes issued				292,500,000	0	0							145,100,000
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
Credit facility, amount repaid				271,015,000	838,705,000	685,928,000											51,000,000
Credit facility, maturity date		Aug. 03, 2012																	Aug. 03, 2012	May 08, 2017					May 08, 2019
Credit facility, borrowing capacity							200,000,000											175,000,000	100,000,000	150,000,000		150,000,000	200,000,000	10,000,000					75,000,000	150,000,000	15,000,000
Credit facility, interest rate above basis																										4.75%	3.75%									1.75%	0.75%									2.25%	1.25%
Credit facility, unused line fee monthly payment																				0.375%
Line of Credit Facility, Current Borrowing Capacity	150,000,000						150,000,000												23,000,000																								10,000,000								15,000,000
Line of Credit Facility, Expiration Date	Jun. 28, 2016			Jun. 28, 2016
Line Of Credit Facility Replacement Of Previous Revolving Credit Amount							100,000,000
Line Of Credit Facility Current Borrowing Capacity Before Amendment	150,000,000							150,000,000
Line Of Credit Facility Current Borrowing Capacity After Amemdment				175,000,000				175,000,000
Line Of Credit Facility Current Borrowing Capacity Increase Decrease For Period																																25,000,000									50,000,000
Required minimum fixed charge coverage ratio when availability under the Revolver is less than 12.5% of the total revolving commitment																																			1										1.1
Excess availability as a percentage of total revolving commitment below which minimum fixed charge coverage ratio maintained																				12.50%
Availability Percentage Threshold Of Total Revolving Commitment Below Which Amounts In Deposit Accounts Will Be Transferred Daily In To Blocked Account																				15.00%
Debt Instrument, Unused Borrowing Capacity, Amount				40,000,000
Dividends, Cash																																										20,000,000
Employee Stock Ownership Plan (ESOP), Repurchase Obligation Amount																																										2,500,000
Long-term Debt, Gross				65,000,000	55,000,000																65,000,000
Line of Credit Facility, Remaining Borrowing Capacity				228,500,000	125,700,000														15,000,000
Line of Credit Facility, Amount Outstanding					65,000,000															25,000,000								300,000,000
Interest Paid																									10,900,000
Repayments of Long-term Debt																									2,300,000
Long-term Debt				450,250,000	65,000,000																				297,800,000
Amortization of Debt Discount (Premium)																									600,000
Interest Coverage Ratio																									6.9													2	3	4
Senior Leverage Ratio																									1.5																							4.5	4	3.5
Line Of Credit Facility Potential Term Extension Period																									91 days
Debt Amortization Percentage																									1.00%
Proceeds from Sale of Productive Assets																									1,000,000
London Interbank Offered Rate Interest Rate Floor																									1.25%
Current portion of long-term debt				3,381,000	0																				3,000,000
Debt issuance costs paid				5,134,000	1,989,000	0																			7,500,000
Pre Amendment Line Of Credit Facility Revolver Increase Borrowing Capacity																																		25,000,000										50,000,000
Post Amendment Line Of Credit Facility Revolver Increase Borrowing Capacity																		25,000,000
Line of Credit Facility, Covenant Terms			(i) no default was or events of default were in existence or would have been caused by such purchase, redemption or payment, (ii) immediately after such purchase, redemption or payment, the Company had unused availability of at least $40 million, (iii) the amount of all cash dividends paid by the Company did not exceed $20 million in any fiscal year and (iv) at least 5 business days prior to the purchase, redemption or payment, an officer of the Company delivered a certificate to its lenders certifying that the conditions precedent in clauses (i)-(iii) have been satisfied.																if the availability under the Company's revolving credit facility was less than $15.0 million at any time before the earlier of August 14, 2011 or the date that monthly financial statements were delivered for the month ending June 30, 2011, the Company could have been required to maintain a varying minimum EBITDA and would have been restricted in the amount of capital expenditures the Company could have made during such period. If the Company's availability was less than $20.0 million thereafter, it would have been required to maintain a fixed charge coverage ratio for the 12 month period ending on the last day of the calendar month that ended most recently prior to such time of not less than 1.1 to 1.0.
Stock Repurchase Program, Authorized Amount			2,500,000
Proceeds from Other Debt									2,500,000
Other Long-term Debt										2,500,000
Other Long-term Debt, Current										$ 400,000