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Debt and Financing Arrangements (Bank Debt) - Additional Information (Detail)
$ in Thousands
6 Months Ended
Jun. 30, 2015
USD ($)
Bank
Mar. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Debt Instrument [Line Items]      
Unsecured credit facility   $ 400,000  
Group of participating banks | Bank 8    
Outstanding balance under applicable credit facility $ 153,000   $ 107,400
Credit facility termination date Jul. 28, 2014    
Approximately available funds under credit facility $ 139,500    
Credit Facility [Member]      
Debt Instrument [Line Items]      
Unsecured credit facility 400,000    
Letter of Credit and Performance Guarantee [Member]      
Debt Instrument [Line Items]      
Outstanding letters of credit and performance guarantees $ 4,200