Debt (Tables)

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Summary of debt

A summary of our outstanding unsecured notes is as follows (amounts in millions):

				At December 31, 2020				At December 31, 2019
Unsecured Senior Notes	Interest Rate	Semi-Annual Interest Payments Due On	Maturity	Principal		Fair Value (Level 2)		Principal		Fair Value (Level 2)
2021 Notes	2.30%	Mar. 15 & Sept. 15	Sept. 2021	$	—	$	—	$	650	$	653
2022 Notes	2.60%	Jun. 15 & Dec. 15	Jun. 2022	—		—		400		405
2026 Notes	3.40%	Mar. 15 & Sept. 15	Sept. 2026	850		970		850		893
2027 Notes	3.40%	Jun. 15 & Dec. 15	Jun. 2027	400		454		400		417
2030 Notes	1.35%	Mar. 15 & Sept. 15	Sept. 2030	500		490		—		—
2047 Notes	4.50%	Jun. 15 & Dec. 15	Jun. 2047	400		525		400		456
2050 Notes	2.50%	Mar. 15 & Sept. 15	Sept. 2050	1,500		1,462		—		—
Total gross long-term debt				$	3,650			$	2,700
Unamortized discount and deferred financing costs				(45)				(25)
Total net carrying amount				$	3,605			$	2,675