Revisions of Prior Period Financial Statements Consolidated Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net earnings	$ 76,201	$ 90,619	$ 85,159	$ 52,789	$ 11,079	$ 83,617	$ 75,385	$ 48,260	$ 304,768	$ 218,341	$ 237,871
Depreciation expense									1,139,922	1,057,813	983,610
Accrued expenses and other non-current liabilities									(18,751)	(53,109)	(64,423)
Net cash provided by operating activities from continuing operations									1,441,788	1,382,818	1,251,811
Debt proceeds									1,283,223	965,533	556,989
Debt repaid, including capital lease obligations									(798,311)	(293,488)	(379,189)
Net cash provided by financing activities from continuing operations									731,485	311,650	347,070
Purchases of property and revenue earning equipment									(2,667,978)	(2,259,164)	(2,122,628)
Sale and leaseback of revenue earning equipment										0	0
Net cash used in investing activities from continuing operations									$ (2,161,355)	(1,704,510)	(1,603,818)
As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net earnings										218,600	237,800
Depreciation expense										1,040,300	957,100
Accrued expenses and other non-current liabilities										(48,700)	(66,600)
Net cash provided by operating activities from continuing operations										1,370,000	1,223,100
Debt proceeds										839,700	557,000
Debt repaid, including capital lease obligations										(280,700)	(332,600)
Net cash provided by financing activities from continuing operations										198,700	393,600
Purchases of property and revenue earning equipment										(2,259,200)	(2,140,500)
Sale and leaseback of revenue earning equipment										125,800	0
Net cash used in investing activities from continuing operations										(1,578,700)	(1,621,700)
Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net earnings										(300)	100
Depreciation expense										17,600	26,500
Accrued expenses and other non-current liabilities										(4,400)	2,200
Net cash provided by operating activities from continuing operations										12,800	28,700
Debt proceeds										125,800	0
Debt repaid, including capital lease obligations										(12,800)	(46,600)
Net cash provided by financing activities from continuing operations										113,000	(46,500)
Purchases of property and revenue earning equipment										0	17,900
Sale and leaseback of revenue earning equipment										(125,800)	0
Net cash used in investing activities from continuing operations										$ (125,800)	$ 17,900