Income Taxes (Details 3) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred income tax assets:
Self-insurance accruals	$ 107,252	$ 93,352
Net operating loss carryforwards	396,313	429,458
Alternative minimum taxes	13,901	10,727
Accrued compensation and benefits	81,454	76,363
Federal benefit on state tax positions	19,247	18,912
Pension benefits	162,141	148,671
Miscellaneous other accruals	28,313	32,763
Deferred tax assets gross	808,621	810,246
Valuation allowance	(16,387)	(14,991)
Deferred tax assets net	792,234	795,255
Deferred income tax liabilities:
Property and equipment basis difference	(2,451,151)	(2,362,194)
Other	(20,735)	(20,583)
Deferred Tax Liabilities, Gross	(2,471,886)	(2,382,777)
Net deferred income tax liability	(1,679,652)	$ (1,587,522)
Deferred tax assets direct financing leases and other assets	$ 9,000