Consolidated Condensed Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Assets:
Accumulated depreciation on revenue earning equipment	$ (3,606,535)	$ (3,596,102)
Accumulated depreciation on operating property and equipment	1,023,020	991,117
Allowance for doubtful accounts, current	$ 18,070	$ 16,955
Shareholders’ equity:
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares authorized	3,800,917	3,800,917
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.5	$ 0.5
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares outstanding	53,039,595	53,335,386