Stock-Based Compensation - Additional Information (Detail) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended			9 Months Ended		1 Months Ended					9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended		1 Months Ended	3 Months Ended		9 Months Ended		1 Months Ended	9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended
	Mar. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Aug. 31, 2013 Employee Stock Purchase Plan ("ESPP") [Member]	Feb. 28, 2013 Employee Stock Purchase Plan ("ESPP") [Member]	Aug. 31, 2012 Employee Stock Purchase Plan ("ESPP") [Member]	Feb. 29, 2012 Employee Stock Purchase Plan ("ESPP") [Member]	May 31, 1998 Employee Stock Purchase Plan ("ESPP") [Member]	Sep. 30, 2013 Employee Stock Purchase Plan ("ESPP") [Member]	Dec. 31, 2012 Employee Stock Purchase Plan ("ESPP") [Member]	Sep. 30, 2013 Service Based Restricted Stock Units [Member]	Sep. 30, 2012 Service Based Restricted Stock Units [Member]	Sep. 30, 2013 Service Based Restricted Stock Units [Member]	Sep. 30, 2012 Service Based Restricted Stock Units [Member]	Jul. 31, 2010 Stock Plans [Member]	Sep. 30, 2013 Stock Plans [Member]	Sep. 30, 2012 Stock Plans [Member]	Sep. 30, 2013 Stock Plans [Member]	Sep. 30, 2012 Stock Plans [Member]	Apr. 30, 2013 Retention Stock Options [Member] Executive Officer [Member]	Sep. 30, 2013 Retention Stock Options [Member] Executive Officer [Member]	Sep. 30, 2013 Retention Stock Options [Member] Minimum [Member] Executive Officer [Member]	Sep. 30, 2013 Retention Stock Options [Member] Maximum [Member] Executive Officer [Member]	Sep. 30, 2013 Restricted Stock [Member]	Sep. 30, 2012 Restricted Stock [Member]	Sep. 30, 2013 Restricted Stock [Member]	Sep. 30, 2012 Restricted Stock [Member]	Sep. 30, 2013 Performance Units [Member]	Sep. 30, 2013 Performance Units [Member]	Sep. 30, 2012 Performance Units [Member]	Sep. 30, 2013 Time Based Restricted Stock Units [Member]	Sep. 30, 2013 Time Based Restricted Stock Units [Member]	Sep. 30, 2012 Time Based Restricted Stock Units [Member]	Sep. 30, 2013 Restricted Stock Units [Member]	Sep. 30, 2012 Restricted Stock Units [Member]	Sep. 30, 2013 Employee Withholding Taxes on Stock Awards [Member]	Sep. 30, 2012 Employee Withholding Taxes on Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based expense		$ 900,000		$ 700,000	$ 2,600,000	$ 2,300,000																					$ 500,000	$ 600,000	$ 1,900,000	$ 2,100,000
Compensation expense for share-based payments		897,000		695,000	2,619,000	2,335,000													400,000	100,000	700,000	200,000
Grants vesting period																4 years									2 years	4 years			4 years
Restricted stock awards issued														10,580		23,982	229,950												23,982					0		5,000
Fair value of options issued														93,000		198,000	1,600,000																			35,000
Restricted stock awards cancellation														10,172	22,850	19,533	75,506												19,533		0	147,250	11,320		1,125		1,125
Grant date fair value of restricted stock cancelled														68,000	100,000	130,000	500,000															1,000,000	79,000		8,000		25,000
Shares, other than options, vested														7,973	2,475	360,538	468,730												360,538				4,836				3,850	2,600
Grant date fair value of restricted stock vested														52,000	17,000	2,100,000	2,800,000
Restricted shares vested grant date intrinsic value														67,000	17,000	2,700,000	3,500,000																36,000				28,000	20,000
Unrecognized compensation expense																			2,000,000		2,000,000						2,000,000		2,000,000								29,000
Weighted average period																					1 year 7 months 6 days								1 year 2 months 12 days								1 year 6 months
Percent of options vested																					25.00%
Employee stock options vesting provisions, description																					25% vest one year from the date of grant and thereafter in monthly increments over the remaining three years.
Options vested in remaining period																					3 years
Period of termination of employment																					90 days
Stock options granted period																		7 years			10 years
Options granted					693,050														3,500	65,000	693,050	69,500	182,500	182,500									169,650
Weighted average exercise price granted																			3,090		2,870
Proceeds from options exercised																			800,000	8,000	900,000	33,000
Option exercised					116,954														105,113	1,281	116,954	5,000
Intrinsic value																			146,000	1,000	153,000	4,000
Shares expired					109,235														32,817	120,200	144,018	336,692
Weighted average exercise price granted																				$ 2.49		$ 2.51
Lower range of exercise prices					$ 5.50
Upper range of exercise prices					$ 11.84
Intrinsic value based on share price		$ 8.85			$ 8.85
Weighted average grant date fair value																							$ 2.83
Grant date fair value of options granted																																	1,200,000
Grant date fair value of restricted stock vested																																	33,000					16,000
Performance share units converted to restricted stock awards																																	139,150
Percentage of fair market value to determine purchase price											85.00%
Offering period													9 months
Proceeds of from issuance of shares under ESPP							300,000	300,000	300,000	300,000
Options issued							51,735	61,230	56,041	48,032
Rate of discount on fair market value of common stock under ESPP												15.00%
Period of expected life, options granted												5 years
Payment of withholding taxes related to stock awards																																							1,000,000	1,200,000
Repurchase of shares		0	59,510
Repurchase of shares, Amount	5,000,000				435,000
Average price of repurchased share			$ 7.31
Repurchase of shares, outstanding amount					$ 4,600,000