Convertible Senior Notes - Additional Information (Detail) (USD $)	12 Months Ended	0 Months Ended	1 Months Ended	3 Months Ended								12 Months Ended				0 Months Ended	1 Months Ended
	Dec. 31, 2013	Jul. 24, 2013 4.50% Convertible senior notes (due 2014)	Nov. 30, 2009 4.50% Convertible senior notes (due 2014)	Jun. 30, 2013 4.50% Convertible senior notes (due 2014)	Mar. 31, 2013 4.50% Convertible senior notes (due 2014)	Dec. 31, 2012 4.50% Convertible senior notes (due 2014)	Sep. 30, 2012 4.50% Convertible senior notes (due 2014)	Jun. 30, 2012 4.50% Convertible senior notes (due 2014)	Mar. 31, 2012 4.50% Convertible senior notes (due 2014)	Dec. 31, 2011 4.50% Convertible senior notes (due 2014)	Sep. 30, 2011 4.50% Convertible senior notes (due 2014)	Dec. 31, 2013 4.50% Convertible senior notes (due 2014)	Dec. 31, 2012 4.50% Convertible senior notes (due 2014)	Dec. 31, 2011 4.50% Convertible senior notes (due 2014)	Nov. 30, 2009 4.50% Convertible senior notes (due 2014) Scenario, Forecast	Jul. 24, 2013 4.25% Convertible Senior Notes (due 2018)	Jul. 24, 2013 4.25% Convertible Senior Notes (due 2018)	Dec. 31, 2013 4.25% Convertible Senior Notes (due 2018)	Dec. 31, 2012 4.25% Convertible Senior Notes (due 2018)
Debt Instrument [Line Items]
Long term debt, face amount			$ 100,000,000									$ 100,000,000				$ 100,000,000	$ 100,000,000
Debt instrument, interest rate			4.50%			4.50%						4.50%	4.50%			4.25%	4.25%	4.25%	4.25%
Frequency of interest payment			Semi-annually													Semi-annually
Debt instrument, maturity date	Apr. 02, 2013		Nov. 01, 2014									Nov. 01, 2014				Aug. 01, 2018
Conversion rate in share per $1000 principal amount of notes			63.2091												68.8564	114.3674	114.3674
Debt instrument, conversion rate			$ 15.82												$ 14.52	$ 8.74	$ 8.74
Cash dividend on common stock per share paid				$ 0.07	$ 0.07	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10
Dividend payment date				Jul. 01, 2013	Apr. 01, 2013	Jan. 02, 2013	Oct. 01, 2012	Jul. 02, 2012	Apr. 02, 2012	Jan. 03, 2012	Oct. 03, 2011
Net proceeds from debt instrument		96,000,000															100,000,000
Gain on debt extinguishment	84,000																100,000
Debt discount			13,700,000									13,700,000
Interest expenses associated with amortization of equity component												2,000,000	2,700,000	2,700,000
Repurchase of related equity component												2,800,000
Unamortized equity component						5,082,000						902,000	5,082,000
Debt discount written off amount												2,200,000
Debt issuance cost written off amount												600,000
Debt instrument repurchase amount		61,000,000										61,000,000
Long term debt, fair value						$ 107,900,000						$ 37,700,000	$ 107,900,000					$ 97,400,000