Quarterly report pursuant to Section 13 or 15(d)

Equity Transactions - Additional Information (Detail)

v3.10.0.1
Equity Transactions - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]          
Non-cash stock-based compensation expense related to additional paid-in capital $ 0.2 $ 0.3 $ 0.4 $ 1.7  
Scenario, Forecast [Member]          
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]          
Expected dividend payments         $ 6.8