Share Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Two Thousand Four Stock Incentive Plan	Sep. 30, 2012 Two Thousand Four Stock Incentive Plan	Sep. 30, 2013 Two Thousand Four Stock Incentive Plan	Sep. 30, 2012 Two Thousand Four Stock Incentive Plan	Sep. 30, 2013 Stock Options	Sep. 30, 2012 Stock Options	Sep. 30, 2013 Stock Options	Sep. 30, 2012 Stock Options	Sep. 30, 2012 Stock Options Awards That Contain Performance Or Market Conditions	Sep. 30, 2013 Stock Options Awards That Contain Performance Or Market Conditions	Sep. 30, 2013 Restricted Stock	Sep. 30, 2012 Restricted Stock	Sep. 30, 2013 Restricted Stock	Sep. 30, 2012 Restricted Stock	Sep. 30, 2012 1998 ESPP	Sep. 30, 2012 1998 ESPP	Mar. 31, 2013 1998 ESPP Minimum	Dec. 31, 2011 2011 Incentive Plan	Sep. 30, 2013 2011 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock issued upon exercise of outstanding stock options																						7,750,000
Shares remain available for future grant																							1,607,221
Stock compensation expense	$ 1,240,000	$ 1,185,000	$ 3,256,000	$ 5,165,000	$ 1,200,000	$ 1,200,000	$ 3,300,000	$ 5,200,000											$ 100,000	$ 800,000
Stock option compensation cost charged against operations									800,000	300,000	1,800,000	3,500,000	1,000	26,000	500,000	700,000	1,700,000	2,000,000
Unrecognized compensation cost	1,900,000		1,900,000												1,900,000		1,900,000
Unamortized stock option compensation, expected to be recognized over a weighted-average period, years	1 year 10 months 6 days
Income as result of reversal of prior compensation expense				500,000
Options remain unvested	533,000		533,000												1,193,120		1,193,120
Shares of restricted stock issued																242,000	641,933	1,839,000
Total aggregate fair market value of restricted stock issued																400,000	600,000	3,400,000
Total fair value of restricted stock vested																	$ 2,400,000	$ 2,100,000
Employee Stock Purchase Plan, purchase price																					85.00%
Employee Stock Purchase Plan, purchase discount																					5.00%