QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Quarterly Financial Information [Line Items]
Revenues	$ 452,607	$ 248,563	$ 290,560	$ 661,000	$ 464,466	$ 238,280	$ 292,521	$ 638,464	$ 1,647,479	$ 1,626,618
Operating income	81,971	38,777	46,891	127,619	80,855	36,241	41,043	130,290	295,258	288,429	$ 316,728
Net income	$ 51,162	$ 17,457	$ 24,470	$ 93,660	$ 44,704	$ 16,276	$ 20,419	$ 90,835	$ 186,749	$ 172,234	$ 162,995
Basic	$ 0.97	$ 0.33	$ 0.46	$ 1.77	$ 0.85	$ 0.31	$ 0.39	$ 1.73	$ 3.53	$ 3.27	$ 3.10
Diluted	$ 0.96	$ 0.33	$ 0.46	$ 1.76	$ 0.84	$ 0.31	$ 0.39	$ 1.72	$ 3.51	$ 3.25	$ 3.08