Quarterly report pursuant to Section 13 or 15(d)

STOCKHOLDERS' EQUITY - Summary of Changes in Shareholders' Equity (Details)

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STOCKHOLDERS' EQUITY - Summary of Changes in Shareholders' Equity (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]        
Beginning balance (in shares)     39,669,094  
Beginning balance     $ 1,258,937 $ 1,109,489
Net earnings $ 39,878 $ 29,133 60,847 45,533
Exercise/vesting of stock-based awards     232 2,839
Excess income tax provision from stock-based awards     (526) 2,012
Stock-based compensation expense     $ 7,313 8,465
Ending balance (in shares) 40,018,044   40,018,044  
Ending balance $ 1,326,803 $ 1,168,338 $ 1,326,803 $ 1,168,338
Common Stock [Member]        
Increase (Decrease) in Stockholders' Equity [Roll Forward]        
Beginning balance (in shares)     39,669,000 39,147,000
Beginning balance     $ 397 $ 391
Exercise/vesting of stock-based awards (in shares)     349,000 514,000
Exercise/vesting of stock-based awards     $ 3 $ 6
Ending balance (in shares) 40,018,000 39,661,000 40,018,000 39,661,000
Ending balance $ 400 $ 397 $ 400 $ 397
Additional Paid-in Capital [Member]        
Increase (Decrease) in Stockholders' Equity [Roll Forward]        
Beginning balance     559,492 538,788
Exercise/vesting of stock-based awards     229 2,833
Excess income tax provision from stock-based awards     (526) 2,012
Stock-based compensation expense     7,313 8,465
Ending balance 566,508 552,098 566,508 552,098
Retained Earnings [Member]        
Increase (Decrease) in Stockholders' Equity [Roll Forward]        
Beginning balance     699,048 570,310
Net earnings     60,847 45,533
Ending balance $ 759,895 $ 615,843 $ 759,895 $ 615,843