Accounting Policies - Additional Information (Detail) (USD $)	6 Months Ended						9 Months Ended	12 Months Ended
	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Sep. 30, 2010	Dec. 31, 2012 Y	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary Of Significant Accounting Policies [Line Items]
Depreciation over life to cost of revenues and selling and administrative expenses, years								6
Net book value of internally manufactured test systems sold								$ 6,000,000	$ 7,800,000	$ 12,200,000
Common stock purchase percentage								100.00%
Grant date time period,maximum								7 years
Restricted stock unit awards granted								4 years
Restricted stock unit award granted after one year								1 year
Award vesting on the first anniversary								100.00%
Regular payroll deductions under ESPP	10.00%							10.00%
Maximum of shares value authorized for purchase								25,000
Maximum shares based compensation	6,000							6,000
Fair market value common stock price percentage								85.00%
Common stock price, percentage								85.00%
Stock options granted	200,000		100,000		300,000			200,000	100,000	300,000
Weighted average grant date fair value	$ 3.42	$ 4.09	$ 4.01	$ 3.66	$ 2.77	$ 3.05		$ 6.85	$ 6.74	$ 4.10
Number of shares available for grant	6,414,000		8,205,000		9,851,000			6,414,000	8,205,000	9,851,000	12,653,000
Discrete benefit not recognized	17,467,000		19,678,000		12,028,000			17,467,000	19,678,000	12,028,000	12,767,000
Advertising costs								1,600,000	1,000,000	600,000
Gains and losses on foreign exchange contracts								4,500,000	900,000	2,500,000
Exercise price							$ 5.48
Call option, shares							34,700,000
Warrant price								$ 7.67
Discrete Tax
Summary Of Significant Accounting Policies [Line Items]
Discrete benefit not recognized	$ 7,000,000							$ 7,000,000
Employee Stock Purchase Plan
Summary Of Significant Accounting Policies [Line Items]
Common stock price, percentage								85.00%
Number of shares available for grant	2,800,000							2,800,000
Minimum
Summary Of Significant Accounting Policies [Line Items]
Grant date time period, minimum								4 years