Annual report pursuant to Section 13 and 15(d)

Shareholders' Equity, Stock Options and Net Income per Share - Net Income per Share (Details)

v3.6.0.2
Shareholders' Equity, Stock Options and Net Income per Share - Net Income per Share (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]                      
Net income and comprehensive income $ 12,706 $ 11,931 $ (10,066) $ 13,099 $ 23,228 $ 15,687 $ 11,824 $ 4,836 $ 27,670 $ 55,575 $ 61,169
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic                 (212) (369) (404)
Numerator for net income and comprehensive income to common shareholders                 $ 27,458 $ 55,206 $ 60,765
Denominator for basic income per share - weighted-average shares                 30,283 30,728 30,599
Denominator for diluted income per share - adjusted weighted-average shares                 30,444 31,040 31,072
Basic net income per share $ 0.42 $ 0.39 $ (0.33) $ 0.43 $ 0.75 $ 0.51 $ 0.38 $ 0.16 $ 0.91 $ 1.80 $ 1.99
Diluted net income per share $ 0.42 $ 0.39 $ (0.33) $ 0.43 $ 0.75 $ 0.50 $ 0.38 $ 0.16 $ 0.90 $ 1.78 $ 1.96
Total number anti-dilutive options and non-vested shares excluded from income per diluted share computation                 310 208 99
Equity Option [Member]                      
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]                      
Weighted Average Number Diluted Shares Outstanding Adjustment                 130 277 431
Total number anti-dilutive options and non-vested shares excluded from income per diluted share computation                 310 184 99
Key Employee Performance Share Based Plan [Member]                      
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]                      
Weighted Average Number Diluted Shares Outstanding Adjustment                 31 35 42
Total number anti-dilutive options and non-vested shares excluded from income per diluted share computation                   24