Investments (Tables)

6 Months Ended

Jun. 30, 2021

Investments [Abstract]

Amortized Cost and Fair Value of the Trust Investments

		Amortized Cost				Fair Value
	Longest	June 30,		December 31,		June 30,		December 31,
(in millions)	Maturity Dates	2021		2020		2021		2020
Stocks	—		N/A		N/A	$	1,905	$	1,908
Municipal bonds	2054	$	896	$	1,013		1,070		1,218
U.S. government and agency securities	2067		942		740		1,048		864
Corporate bonds	2070		442		460		518		550
Short-term investments and receivables/payables1	One-year		331		281		345		293
Total		$	2,611	$	2,494	$	4,886	$	4,833

1 Short-term investments include $52 million and $138 million of repurchase agreements payable by financial institutions which earn interest, are fully secured by U.S. Treasury securities and mature by July 1, 2021 and January 4, 2021 as of June 30, 2021 and December 31, 2020, respectively.

Summary of gains and losses

	Three months ended June 30,				Six months ended June 30,
(in millions)	2021		2020		2021		2020
Gross realized gains	$	140	$	75	$	251	$	114
Gross realized losses		(4)		(1)		(16)		(3)
Net unrealized gains (losses) for equity securities		16		271		34		(105)