Consolidated Condensed Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets:
Receivables, net of allowance of $13,192 and $14,915, respectively	$ 13,192	$ 14,915
Operating property and equipment, net of accumulated depreciation of $1,187,188 and $1,128,040, respectively	1,187,188	1,128,040
Intangible assets, net of accumulated amortization of $55,934 and $51,578, respectively	$ 55,934	$ 51,578
Shareholders’ equity:
Preferred stock, shares authorized (in shares)	3,800,917	3,800,917
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.50	$ 0.50
Common stock, shares authorized (in shares)	400,000,000	400,000,000
Common stock, shares outstanding (in shares)	52,947,715	53,463,118