Convertible Debentures and Credit Arrangements - Credit Arrangements - Additional Information (Detail) (Credit Arrangements, USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Debt Instrument [Line Items]
Maximum aggregate amount of revolving credit facility in the form of borrowings, guarantees and issuances of letters of credit (subject to a $20 million sublimit)	$ 50
Sublimit facility attached on revolving credit facility	20
Amount of depository, operating accounts, the lesser and investment and securities accounts required to be maintained at the lending bank	80
Percentage of depository, operating accounts, the lesser and investment and securities accounts required to be maintained at the lending bank	75.00%
Amount available for borrowing under revolving credit facility	43.7
After Amendment
Debt Instrument [Line Items]
Credit facility maturity date	Dec. 31, 2014
Landlord of CompuCom Systems
Debt Instrument [Line Items]
Letter of credit under the credit facility	$ 6.3
Letter of credit expiration date	Mar. 19, 2019