XML 62 R44.htm IDEA: XBRL DOCUMENT v3.8.0.1
Estimated Fair Value of Long Term Debt (Detail) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Fair Value, Inputs, Level 2    
Debt Instrument [Line Items]    
Estimated Fair Value of Long-Term Debt $ 457.1 $ 370.3