CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ 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
CONSOLIDATED STATEMENTS OF OPERATIONS
REVENUES	$ 717,418	$ 787,563	$ 771,490	$ 711,839	$ 774,279	$ 826,158	$ 793,350	$ 700,001	$ 2,988,310	$ 3,093,788	$ 2,826,457
OPERATING EXPENSES	728,647	756,355	736,290	703,248	737,117	770,103	790,194	687,276	2,924,540	2,984,690	2,765,109
OPERATING INCOME	(11,229)	31,208	35,200	8,591	37,162	56,055	3,156	12,725	63,770	109,098	61,348
OTHER INCOME (COSTS)
Interest and dividend income									6,453	3,914	1,293
Interest and other related financing costs									(11,467)	(9,468)	(6,342)
Other, net									(7,285)	(19,158)	(4,723)
TOTAL OTHER INCOME (COSTS)	(798)	(7,866)	(1,640)	(1,995)	(16,492)	(2,064)	(2,422)	(3,734)	(12,299)	(24,712)	(9,772)
INCOME BEFORE INCOME TAXES									51,471	84,386	51,576
INCOME TAX PROVISION (BENEFIT)	(6,478)	7,072	9,184	1,708	5,371	13,215	(499)	(963)	11,486	17,124	(8,150)
NET INCOME	$ (5,549)	$ 16,270	$ 24,376	$ 4,888	$ 15,299	$ 40,776	$ 1,233	$ 9,954	$ 39,985	$ 67,262	$ 59,726
EARNINGS PER COMMON SHARE(1)
Basic (in dollars per share)	$ (0.22)	$ 0.64	$ 0.95	$ 0.19	$ 0.59	$ 1.58	$ 0.05	$ 0.39	$ 1.56	$ 2.61	$ 2.32
Diluted (in dollars per share)	$ (0.22)	$ 0.62	$ 0.92	$ 0.18	$ 0.57	$ 1.52	$ 0.05	$ 0.37	$ 1.51	$ 2.51	$ 2.25
AVERAGE COMMON SHARES OUTSTANDING
Basic (in shares)	25,490,393	25,527,982	25,554,286	25,570,415	25,707,335	25,697,509	25,670,325	25,642,871	25,535,529	25,679,736	25,683,745
Diluted (in shares)	25,490,393	26,416,595	26,431,592	26,512,349	26,682,262	26,795,659	26,699,549	26,596,376	26,450,055	26,698,831	26,424,389
CASH DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.32	$ 0.32	$ 0.32