Property and Equipment (Tables)

The components of property and equipment, excluding amounts transferred to held for sale, were as follows:


(in millions)	Useful Lives	December 31, 2023		December 31, 2022

Land		$	72	$	109
Buildings and equipment	Up to 30 years	4,465		4,659
Wireless communications systems	Up to 20 years	65,628		61,738
Leasehold improvements	Up to 10 years	2,489		2,326
Capitalized software	Up to 10 years	22,573		20,342
Leased wireless devices	Up to 16 months	400		1,415
Construction in progress	N/A	3,286		4,599
Accumulated depreciation and amortization		(58,481)		(53,102)

Property and equipment, net		$	40,432	$	42,086

Activity in our asset retirement obligations was as follows:


(in millions)	Year Ended December 31, 2023		Year Ended December 31, 2022

Asset retirement obligations, beginning of year	$	1,852	$	1,899

Liabilities incurred	28		10
Liabilities settled	(399)		(379)
Accretion expense	71		65
Changes in estimated cash flows	164		292
Transfers to held for sale	—		(35)

Asset retirement obligations, end of period	$	1,716	$	1,852

Classified on the consolidated balance sheets as:

Other current liabilities	$	133	$	267
Other long-term liabilities	1,583		1,585