Annual report pursuant to Section 13 and 15(d)

Capital Structure and Per Share Data - Dilutive Effect on Earnings Per Share (Detail)

v3.8.0.1
Capital Structure and Per Share Data - Dilutive Effect on Earnings Per Share (Detail) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Earnings Per Share [Abstract]                      
Weighted Average Shares, Basic                 43,997 45,637 50,489
Weighted Average Shares, Stock compensation plans                 361 311 394
Weighted Average Shares, Diluted                 44,358 45,948 50,883
Income (Loss) From Continuing Operations, Amount                 $ 94,153 $ 94,516 $ 88,091
Participating securities income (loss) from continuing operations non-vested restricted stock and restricted stock units                 (85) (52) (36)
Income (Loss) From Continuing Operations, Basic, Amount                 94,068 94,464 88,055
Income (Loss) From Continuing Operations Diluted, Amount                 $ 94,068 $ 94,464 $ 88,055
Income (Loss) From Continuing Operations, Basic, Per Share Amount                 $ 2.14 $ 2.07 $ 1.74
Income (Loss) From Continuing Operations, Diluted, Per Share Amount                 $ 2.12 $ 2.06 $ 1.73
Income (Loss) From Discontinued Operations, Earnings (loss), Amount                 $ (1,170) $ (1,323) $ (1,780)
Income (Loss) From Discontinued Operations, Basic earnings (loss), Amount                 (1,170) (1,323) (1,780)
Income (Loss) From Discontinued Operations, Diluted earnings (loss), Amount                 $ (1,170) $ (1,323) $ (1,780)
Income (Loss) From Discontinued Operations, Basic earnings (loss), Per Share Amount                 $ (0.03) $ (0.03) $ (0.03)
Income (Loss) From Discontinued Operations, Diluted earnings (loss), Per Share Amount                 $ (0.03) $ (0.03) $ (0.03)
Net Income (Loss), Amount $ 61,952 $ 19,440 $ 12,132 $ (541) $ 37,636 $ 18,111 $ 22,822 $ 14,624 $ 92,983 $ 93,193 $ 86,311
Participating securities net income (loss) non-vested restricted stock and restricted stock units                 (85) (52) (36)
Net Income (Loss), Basic, Amount                 92,898 93,141 86,275
Net Income (Loss), Diluted, Amount                 $ 92,898 $ 93,141 $ 86,275
Net Income (Loss), Basic, Per Share Amount $ 1.43 $ 0.45 $ 0.27 $ (0.01) $ 0.84 $ 0.40 $ 0.50 $ 0.31 $ 2.11 $ 2.04 $ 1.71
Net Income (Loss), Diluted, Per Share Amount $ 1.42 $ 0.44 $ 0.27 $ (0.01) $ 0.83 $ 0.40 $ 0.50 $ 0.31 $ 2.09 $ 2.03 $ 1.70