XML 60 R49.htm IDEA: XBRL DOCUMENT v3.8.0.1
Long-Term Debt and Short-Term Borrowings - Revolving Credit Facility - Additional Information (Detail) - USD ($)
Mar. 31, 2018
Dec. 31, 2017
Debt Instrument [Line Items]    
Revolving credit facility $ 463,000,000  
Letters of credit outstanding amount 69,300,000  
2017 Credit Agreement [Member] | Revolving credit facility [Member]    
Debt Instrument [Line Items]    
Revolving credit facility 463,000,000 $ 0
Letters of credit outstanding amount $ 2,000,000 $ 2,000,000