Debt - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended							6 Months Ended	1 Months Ended	6 Months Ended			3 Months Ended	6 Months Ended	0 Months Ended		6 Months Ended			6 Months Ended		1 Months Ended	6 Months Ended					1 Months Ended		6 Months Ended	1 Months Ended	6 Months Ended		6 Months Ended							6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Loan Agreement	Nov. 27, 2012 Loan Agreement	Jun. 30, 2013 Convertible Senior Notes	Apr. 25, 2013 Convertible Senior Notes	Jun. 30, 2013 Amended and Restated Credit Agreement	Apr. 23, 2012 Unsecured Debt Convertible Senior Notes	Jun. 30, 2013 Unsecured Debt Convertible Senior Notes	Jun. 30, 2013 Unsecured Debt Convertible Senior Notes Scenario 1	Jun. 30, 2013 Unsecured Debt Convertible Senior Notes Scenario 2	Jun. 30, 2013 Amended Credit Agreement	Jun. 30, 2013 Amended Credit Agreement	May 08, 2012 Revolving Credit Facility	Jun. 30, 2013 Revolving Credit Facility	Jun. 30, 2013 Revolving Credit Facility Amended and Restated Credit Agreement	Jun. 30, 2013 Revolving Credit Facility Amended and Restated Credit Agreement Option to increase subject to certain conditions	Jun. 30, 2013 Revolving Credit Facility Amended and Restated Credit Agreement Swing Line Loan	Jun. 30, 2013 Revolving Credit Facility Amended and Restated Credit Agreement LIBOR	Jun. 30, 2013 Revolving Credit Facility Amended and Restated Credit Agreement Base Rate	Apr. 25, 2013 Term Loan Credit Facilty	Jun. 30, 2013 Term Loan Credit Facilty	Dec. 31, 2012 Term Loan Credit Facilty	Apr. 25, 2013 Term Loan Credit Facilty Loan Agreement	May 08, 2012 Term Loan Credit Facilty Senior Secured Credit Facility	May 08, 2012 Term Loan Credit Facilty Incremental Senior Credit Facility	Apr. 25, 2013 Term Loan Credit Facilty Amended Credit Agreement	Apr. 25, 2013 Term Loan Credit Facilty Libor	Jun. 30, 2013 Term Loan Credit Facilty Libor	Apr. 25, 2013 Term Loan Credit Facilty Base Rate	Jun. 30, 2013 Term Loan Credit Facilty Base Rate	Jun. 30, 2013 Letter Of Credit Subfacility Revolving Credit Facility Amended and Restated Credit Agreement	Jun. 30, 2013 Minimum Unsecured Debt Convertible Senior Notes Scenario 1	Jun. 30, 2013 Minimum Revolving Credit Facility Amended and Restated Credit Agreement LIBOR	Jun. 30, 2013 Minimum Revolving Credit Facility Amended and Restated Credit Agreement Base Rate	Jun. 30, 2013 Minimum Term Loan Credit Facilty Through September 30, 2013	Jun. 30, 2013 Minimum Term Loan Credit Facilty Thereafter through September 30, 2015	Jun. 30, 2013 Minimum Term Loan Credit Facilty Thereafter	Jun. 30, 2013 Maximum Revolving Credit Facility Amended and Restated Credit Agreement	Jun. 30, 2013 Maximum Term Loan Credit Facilty Through September 30, 2013	Jun. 30, 2013 Maximum Term Loan Credit Facilty Thereafter through September 30, 2015	Jun. 30, 2013 Maximum Term Loan Credit Facilty Thereafter
Notes issued, due date											2018	2018
Notes issued, aggregate principal amount	$ 429,349,000		$ 429,349,000		$ 450,250,000		$ 2,500,000				$ 150,000,000	$ 150,000,000													$ 277,000,000	$ 297,750,000	$ 277,000,000
Notes issued, interest rate							4.25%	3.375%	3.375%		3.375%	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									$ 11.70
Convertible notes, conversation date												Nov. 01, 2017
Number of trading days													30 days																							20 days
Number of consecutive trading days													30 days	0 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			0	292,500,000								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, maturity date																			May 08, 2017					May 08, 2019
Credit facility, borrowing capacity																			150,000,000	200,000,000	10,000,000								75,000,000						15,000,000
Credit facility, interest rate above basis																						2.25%	1.25%								3.50%	4.75%	2.50%	3.75%			1.75%	0.75%
Credit facility, unused line fee monthly payment																			0.375%
Required minimum fixed charge coverage ratio when availability under the Revolver is less than 12.5% of the total revolving commitment																																										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%
Line of Credit Facility, Remaining Borrowing Capacity																		187,700,000
Line of Credit Facility, Amount Outstanding																			25,000,000									300,000,000		297,000,000
Interest Paid																8,500,000
Repayments of Long-term Debt																20,800,000
Long-term debt	397,171,000		397,171,000		416,849,000	2,300,000									277,000,000	277,000,000
Interest coverage ratio																																							2	3	4
Senior leverage ratio																																					1.0		1.0	1.0	1.0		4.5	4.0	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 foor																									1.25%
Current portion of long-term debt	3,923,000		3,923,000		3,381,000	500,000									3,500,000	3,500,000
Debt issuance costs paid			981,000	5,026,000												8,500,000
Interest expense	6,577,000	5,441,000	14,112,000	6,174,000											400,000	400,000
Line of credit facility, decrease, repayments			$ 651,000	$ 234,180,000													$ 51,000,000													$ 20,000,000
Percentage of tranche loan amount on equal quarterly installments																								0.25%
Senior secured leverage ratio										1.6:1.0