Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Summary of Significant Accounting Policies

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

	2019			2018			2017
Increase (decrease) in operating expenses	$	9		$	(2)		$	—
Risk-free discount rate applied to environmental remediation liabilities and recovery assets		1.75	%		2.75	%		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

	2019		2018
Equity method investments	$	377	$	257
Investments without readily determinable fair values		57		83
Redeemable preferred stock		49		66
Investments in unconsolidated entities	$	483	$	406

Schedule of Supplemental Cash Flow Information

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

	2019		2018		2017
Interest, net of capitalized interest	$	397	$	339	$	380
Income taxes		292		349		562