Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
REVENUES	$ 436,393	$ 463,331	$ 882,077	$ 910,716
EXPENSES:
Operating	307,897	316,446	623,200	630,364
General and administrative	26,417	27,364	51,243	53,844
Depreciation and amortization	36,800	42,345	73,057	84,404
Asset impairments			259
Costs and Expenses, Total	371,114	386,155	747,759	768,612
OPERATING INCOME	65,279	77,176	134,318	142,104
OTHER (INCOME) EXPENSE:
Interest expense, net	16,622	16,796	33,112	34,340
Other (income) expense	(60)	132	(43)	49
Total non-operating expense (income)	16,562	16,928	33,069	34,389
INCOME BEFORE INCOME TAXES	48,717	60,248	101,249	107,715
Income tax expense	(3,242)	(2,665)	(5,727)	(3,825)
NET INCOME	$ 45,475	$ 57,583	$ 95,522	$ 103,890
BASIC EARNINGS PER SHARE	$ 0.38	$ 0.49	$ 0.81	$ 0.89
DILUTED EARNINGS PER SHARE	0.38	0.49	0.81	0.88
DIVIDENDS DECLARED PER SHARE	$ 0.42	$ 0.54	$ 0.84	$ 1.08