Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	0 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2013	Sep. 30, 2014 Investment	Sep. 30, 2013	Sep. 30, 2014 Investment	Sep. 30, 2013	Dec. 31, 2013 Investment	Aug. 07, 2012
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of business	$ 54.5
Cash in banks		37.5		37.5		35.2
Money market mutual funds		61.8		61.8		41.8
Number of money market mutual fund invested		3		3		3
Maximum term for investments to be considered cash equivalents days				90
Undistributed earnings (loss) allocable to participating securities		0.1	0.1	0.3
Share-based expense		1.2	1.3	3.3	5.2
Stock repurchase program, repurchase authorized							50.0
Stock repurchase program, shares repurchased					0.3
Stock repurchase program, shares repurchased amount					1.6
Stock repurchased during period, average cost per share					$ 5.80
Maximum
Summary Of Significant Accounting Policies [Line Items]
Undistributed earnings (loss) allocable to participating securities					$ 0.1
Share-based awards
Summary Of Significant Accounting Policies [Line Items]
Anti-dilutive securities not included in the computation of diluted earnings per share		1.5	2.4	1.5	2.4
Network Equipment And Tools And Test Equipment
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives, years				5 years
Furniture and fixtures
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives, years				3 years
Leasehold Improvements
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives, description				Five years or the life of the lease, whichever is less