THREE-FOR-TWO STOCK SPLIT - Effects of Stock Split on Earnings Per Share (Details) - 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	Dec. 31, 2014
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
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—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
Shares used for computation:
Weighted average shares outstanding - basic (in shares)									217,988	218,244	218,583	218,695
Weighted average shares outstanding - diluted (in shares)									217,988	218,244	218,583	218,695
Pro forma
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income												$ 137,664
Income per share—Basic (in dollars per share)												$ 0.94
Income per share—Diluted (in dollars per share)												$ 0.94
Shares used for computation:
Weighted average shares outstanding - basic (in shares)												145,796
Weighted average shares outstanding - diluted (in shares)												145,796
Adjustment
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income												$ 0
Income per share—Basic (in dollars per share)												$ (0.31)
Income per share—Diluted (in dollars per share)												$ (0.31)
Shares used for computation:
Weighted average shares outstanding - basic (in shares)												72,899
Weighted average shares outstanding - diluted (in shares)												72,899