Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation Plans - Changes in Company's Common Stock Price During Reporting Period (Detail)

v3.10.0.1
Stock-Based Compensation Plans - Changes in Company's Common Stock Price During Reporting Period (Detail) - Stock Based Compensation Expense [Member] - $ / shares
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Common stock price at beginning of period $ 36.06 $ 24.58 $ 32.61 $ 26.72
Common stock price at end of period 39.01 26.36 39.01 26.36
Increase (decrease) in stock price $ 2.95 $ 1.78 $ 6.40 $ (0.36)