Annual report pursuant to Section 13 and 15(d)

UNAUDITED QUARTERLY DATA (Details)

v3.8.0.1
UNAUDITED QUARTERLY DATA (Details) - USD ($)
$ / shares in Units, $ 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
Dec. 31, 2014
UNAUDITED QUARTERLY DATA                        
Revenues $ 414,713 $ 450,442 $ 433,555 $ 375,247 $ 385,614 $ 423,994 $ 411,133 $ 352,736 $ 1,673,957 $ 1,573,477 $ 1,485,305  
Gross profit (Revenues less cost of services provided) 207,194 231,661 229,075 186,084 192,619 218,386 215,190 174,934        
Net Income $ 33,735 $ 51,430 $ 53,689 $ 40,270 $ 38,007 $ 49,651 $ 47,783 $ 31,928 $ 179,124 $ 167,369 $ 152,149 $ 137,664
Income per share:                        
Income per share—Basic (in dollars per share) $ 0.15 $ 0.24 $ 0.25 $ 0.18 $ 0.17 $ 0.23 $ 0.22 $ 0.15 $ 0.82 $ 0.77 $ 0.70 $ 0.63
Income per share—Diluted (in dollars per share) $ 0.15 $ 0.24 $ 0.25 $ 0.18 $ 0.17 $ 0.23 $ 0.22 $ 0.15 $ 0.82 $ 0.77 $ 0.70 $ 0.63