Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net income	$ 98,825	$ 125,075
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of property, equipment, and intangibles	211,495	196,805
Amortization Of Debt Issuance Costs Original Issue Discount And Losses On Terminated Swaps	996	5,574
Gain on disposal of property and equipment, less write-off of totaled tractors	(14,797)	(21,974)
Impairments	0	1,480
Deferred income taxes	(25,670)	(8,106)
Provision for (reduction of) losses on accounts receivable	(2,626)	5,348
Non-cash loss on debt extinguishment and write-offs of deferred financing costs and original issue discount	0	9,567
Stock-based compensation expense	4,691	4,618
Excess tax benefit from stock-based compensation	(547)	(2,200)
Income effect of mark-to-market adjustment of interest rate swaps	0	87
Increase (decrease) in cash resulting from changes in:
Accounts receivable	21,152	25,328
Inventories and supplies	2,162	(102)
Prepaid expenses and other current assets	(843)	(1,197)
Other assets	2,682	6,583
Accounts payable, and accrued and other liabilities	31,313	10,336
Net cash provided by operating activities	328,833	357,222
Cash flows from investing activities:
Increase in cash and cash equivalents – restricted	(4,246)	(12,832)
Proceeds from maturities of investments	23,869	23,965
Purchases of investments	(23,737)	(22,710)
Proceeds from sale of property and equipment	96,228	76,545
Capital expenditures	(141,269)	(260,858)
Payments received on notes receivable	4,763	3,137
Expenditures on assets held for sale	(24,784)	(19,777)
Payments received on assets held for sale	18,459	8,019
Payments received on equipment sale receivables	0	293
Net cash used in investing activities	(50,717)	(204,218)
Cash flows from financing activities:
Repayment of long-term debt and capital leases	(131,125)	(954,561)
Proceeds from long-term debt	0	684,504
Net (repayments) borrowings on revolving line of credit	(150,000)	143,000
Borrowings under accounts receivable securitization	100,000	65,000
Repayment of accounts receivable securitization	(25,000)	(149,000)
Payment of deferred loan costs	0	(3,240)
Proceeds from common stock issued	6,130	7,667
Repurchases of Class A common stock	(115,000)	0
Excess tax benefit from stock-based compensation	547	2,200
Net cash used in financing activities	(314,448)	(204,430)
Net decrease in cash and cash equivalents	(36,332)	(51,426)
Cash and cash equivalents at beginning of period	107,590	105,132
Cash and cash equivalents at end of period	71,258	53,706
Cash paid during the period for:
Interest	22,818	37,254
Income taxes	67,058	77,335
Non-cash investing activities:
Equipment purchase accrual	29,813	11,801
Notes receivable from sale of assets	1,416	5,618
Equipment sales receivables	0	5
Non-cash financing activities:
Capital lease additions	12,811	142,937
Accrued deferred loan costs	$ 0	$ 250