Consolidated Condensed Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Assets:
Allowance for doubtful accounts, current	$ 15,372	$ 16,388
Revenue earning equipment, accumulated depreciation	3,679,498	3,648,704
Operating property and equipment, accumulated depreciation	$ 1,046,137	$ 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	53,309,221	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