Investments (Tables)

9 Months Ended

Sep. 30, 2021

Investments [Abstract]

Amortized Cost and Fair Value of the Trust Investments

		Amortized Cost				Fair Value
	Longest	September 30,		December 31,		September 30,		December 31,
(in millions)	Maturity Dates	2021		2020		2021		2020
Stocks	—		N/A		N/A	$	1,819	$	1,908
Municipal bonds	2054	$	836	$	1,013		990		1,218
U.S. government and agency securities	2067		1,129		740		1,238		864
Corporate bonds	2070		394		460		459		550
Short-term investments and receivables/payables1	One-year		252		281		263		293
Total		$	2,611	$	2,494	$	4,769	$	4,833

1 Short-term investments include $59 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 October 1, 2021 and January 4, 2021 as of September 30, 2021 and December 31, 2020, respectively.

Summary of gains and losses

	Three months ended September 30,				Nine months ended September 30,
(in millions)	2021		2020		2021		2020
Gross realized gains	$	77	$	51	$	328	$	165
Gross realized losses		(5)		(2)		(21)		(5)
Net unrealized (losses) gains for equity securities		(74)		110		(41)		5