EARNINGS PER SHARE - Summary (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income (Numerator)
Net income	$ 140,997	$ 97,262	$ 327,315	$ 228,234
Less: net income attributable to participating securities	(1,892)	(1,643)	(4,546)	(3,898)
Basic EPS - Income available to common stockholders	139,105	95,619	322,769	224,336
Diluted EPS - Income available to common stockholders and assumed conversions	$ 139,105	$ 95,620	$ 322,770	$ 224,337
Shares (Denominator)
Basic EPS - Income available to common stockholders (shares)	93,728,000	93,402,000	93,713,000	93,396,000
Effects of dilutive securities - options	$ 0	$ 1	$ 1	$ 1
Effects of dilutive securities - options (shares)	31,000	33,000	35,000	35,000
Diluted EPS - Income available to common stockholders and assumed conversions (shares)	93,759,000	93,435,000	93,748,000	93,431,000
Per-Share Amount
Basic EPS - Income available to common stockholders (USD per share)	$ 1.48	$ 1.02	$ 3.44	$ 2.40
Diluted EPS - Income available to common stockholders and assumed conversions (USD per share)	$ 1.48	$ 1.02	$ 3.44	$ 2.40
Excluded antidilutive securities (shares)	292,100	300,500	295,600	255,000