QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 464,693	$ 257,160	$ 181,005	$ 161,679	$ 300,983	$ 258,736	$ 308,639	$ 231,762	$ 1,064,537	$ 1,100,120	$ 1,035,005
Operating income	70,254	42,312	(8,295)	2,539	62,443	24,372	54,133	77,554	106,810	218,502	326,762
Net income	37,924	23,847	(5,879)	1,834	147,328	10,516	3,120	5,659	57,726	166,623	202,326
Net income attributable to common stockholders	$ 37,261	$ 23,365	$ (5,088)	$ 1,474	$ 149,121	$ 10,504	$ 3,120	$ 5,659	$ 57,012	$ 168,404	$ 202,303
Earnings Per Share [Abstract]
Basic earnings (loss) per share: (in dollars per share)	$ 0.87	$ 0.54	$ (0.12)	$ 0.03	$ 3.48	$ 0.25	$ 0.08	$ 0.14	$ 1.32	$ 4.07	$ 5.12
Diluted earnings (loss) per share: (in dollars per share)	$ 0.86	$ 0.54	$ (0.12)	$ 0.03	$ 3.46	$ 0.24	$ 0.07	$ 0.13	$ 1.32	$ 3.91	$ 4.73
Weighted average shares outstanding:
Basic (in shares)	43,075	43,066	42,573	42,976	42,860	42,845	40,373	39,799	43,036	41,364	39,492
Diluted (in shares)	43,250	43,317	42,942	43,363	43,120	43,267	43,051	42,757	43,237	43,089	42,729