Consolidated Condensed Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Assets:
Allowance for doubtful accounts, current	$ 17,180	$ 16,388
Revenue earning equipment, accumulated depreciation	3,811,697	3,689,016
Operating property and equipment, accumulated depreciation	$ 1,068,779	$ 1,035,028
Shareholders’ equity:
Common stock, par value	$ 0.50	$ 0.50
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares outstanding	53,374,025	53,039,688
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares authorized	3,800,917	3,800,917
Preferred stock, shares outstanding	0	0