Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
REVENUES	$ 449,929	$ 436,393	$ 890,845	$ 882,077
EXPENSES:
Operating	320,539	307,897	639,690	623,200
General and administrative	27,538	26,417	52,509	51,243
Depreciation and amortization	38,560	36,800	76,649	73,057
Asset impairments	1,580		1,580	259
Costs and Expenses, Total	388,217	371,114	770,428	747,759
OPERATING INCOME	61,712	65,279	120,417	134,318
OTHER (INCOME) EXPENSE:
Interest expense, net	19,038	16,622	38,074	33,112
Expenses associated with debt refinancing transactions	1,016		1,016
Other (income) expense	33	(60)	(10)	(43)
Total non-operating expense (income)	20,087	16,562	39,080	33,069
INCOME BEFORE INCOME TAXES	41,625	48,717	81,337	101,249
Income tax expense	(2,428)	(3,242)	(4,363)	(5,727)
NET INCOME	$ 39,197	$ 45,475	$ 76,974	$ 95,522
BASIC EARNINGS PER SHARE	$ 0.33	$ 0.38	$ 0.65	$ 0.81
DILUTED EARNINGS PER SHARE	0.33	0.38	0.65	0.81
DIVIDENDS DECLARED PER SHARE	$ 0.43	$ 0.42	$ 0.86	$ 0.84