Annual report pursuant to Section 13 and 15(d)

Share-based Compensation - Summary of Performance Share Award Activity (Detail)

v3.10.0.1
Share-based Compensation - Summary of Performance Share Award Activity (Detail) - Performance Shares [Member] - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Shares      
Nonvested stock, Beginning balance, Shares (in shares) 415,370 556,413 218,840
Granted (in shares) 152,261 98,518 146,916
Earned, Shares 0 65,017 205,833
Vested (in shares) (221,339) (291,859) (5,104)
Unearned or forfeited (in shares) (82,793) (12,719) (10,072)
Nonvested stock, Ending balance, Shares (in shares) 263,499 415,370 556,413
Weighted-Average Grant-Date Fair Value      
Nonvested stock, Beginning balance (in dollars per share) $ 20.76 $ 14.15 $ 13.67
Granted (in dollars per share) 29.25 33.92 26.97
Earned (in dollars per share) 0.00 10.03 5.54
Vested (in dollars per share) 14.78 9.88 11.00
Unearned or forfeited (in dollars per share) 30.80 28.05 16.58
Nonvested stock, Ending balance (in dollars per share) $ 27.54 $ 20.76 $ 14.15