Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Summary of Significant Accounting Policies

Summary of the impact of revisions in risk-free discount rate

The following table summarizes the impacts of revisions in the risk-free discount rate applied to our environmental remediation liabilities and recovery assets for the years ended December 31 (in millions) and the risk-free discount rate applied as of December 31:


	2018			2017			2016
Decrease in operating expenses	$	(2)		$	—		$	(2)
Risk-free discount rate applied to environmental remediation liabilities and recovery assets		2.75	%		2.5	%		2.5	%

Schedule of estimated useful lives

The estimated useful lives for significant property and equipment categories are as follows (in years):


		Useful Lives
Vehicles — excluding rail haul cars		3 to 10
Vehicles — rail haul cars		10 to 30
Machinery and equipment — including containers		3 to 30
Buildings and improvements		5 to 40
Furniture, fixtures and office equipment		3 to 10

Summary of investments in unconsolidated entities

The following table summarizes our investments in unconsolidated entities as of December 31 (in millions):


	2018		2017
Equity method investments	$	257	$	127
Investments without readily determinable fair values		83		87
Redeemable preferred stock		66		55
Investments in unconsolidated entities	$	406	$	269

Schedule of Supplemental Cash Flow Information

The following table shows supplemental cash flow information for the years ended December 31 (in millions):


	2018		2017		2016
Interest, net of capitalized interest	$	339	$	380	$	375
Income taxes		349		562		442