Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax assets:
Financing lease obligations	$ 156,913	$ 165,703
Operating lease obligations	406,172
Operating loss carryforwards	330,983	298,255
Deferred lease liability	0	63,263
Accrued expenses	54,154	61,309
Tax credits	50,356	50,462
Capital loss carryforward	40,723	41,413
Intangible assets	11,160	10,133
Other	8,098	2,872
Total gross deferred income tax asset	1,058,559	693,410
Valuation allowance	(408,903)	(336,417)
Net deferred income tax assets	649,656	356,993
Deferred income tax liabilities:
Property, plant and equipment	(303,853)	(334,145)
Operating lease right-of-use assets	(328,100)
Operating lease right-of-use assets	(33,100)	(41,219)
Total gross deferred income tax liability	(665,053)	(375,364)
Net deferred tax liability	$ (15,397)	$ (18,371)