Debt - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended		6 Months Ended				0 Months Ended	1 Months Ended	6 Months Ended
	Mar. 31, 2009	Mar. 30, 2014	Sep. 30, 2013	Jun. 29, 2014	Jun. 30, 2013	Dec. 31, 2013	Mar. 31, 2009	Mar. 13, 2014 4.50% Convertible Senior Notes Due March 15, 2014	Apr. 30, 2009 4.50% Convertible Senior Notes Due March 15, 2014	Jun. 29, 2014 4.50% Convertible Senior Notes Due March 15, 2014
Debt Instrument
Borrowings from local bank							$ 10,000,000
Term of loan, years	5 years
Debt instrument, interest rate, stated percentage							0.80%		4.50%
Loan collateralized by real estate mortgage							6,000,000
Unsecured loan							4,000,000
Semiannual principal payments of loan		1,000,000	1,000,000
Aggregate principal amount				0		189,998,000			190,000,000
Initial debt conversion price									$ 5.4750
Conversion rate in number of shares									182.65	131.95
Additional aggregate principal amount									1,000
Senior notes maturity date									Mar. 15, 2014
Number of shares excluded for conversion rate calculation										50.7
Trading days used to determine average price per share										25 days
Average trading price of common shares										$ 19.74
Payments of long-term debt				$ 190,975,000	$ 1,063,000					$ 190,000,000
Stock issued in conversion of notes										25,100,000
Stock received and retired								25,100,000
Strike price per share of warrant				$ 7.6389
Warrants settled on a daily basis				536,000
Warrant settlement period				65 days
Common stock shares were issued for warrants exercised				1,900,000