Property and Equipment (Tables)

6 Months Ended

Jun. 30, 2020

The components of property and equipment were as follows:


(in millions)	Useful Lives	June 30, 2020		December 31, 2019

Land		$	236	$	—
Buildings and equipment	Up to 40 years	3,554		2,587
Wireless communications systems	Up to 20 years	43,876		34,353
Leasehold improvements	Up to 12 years	1,666		1,345
Capitalized software	Up to 10 years	15,020		12,705
Leased wireless devices	Up to 19 months	7,605		1,139
Construction in progress		3,933		2,973
Accumulated depreciation and amortization		(37,089)		(33,118)

Property and equipment, net		$	38,801	$	21,984

Activity in our asset retirement obligations was as follows:


(in millions)	Six Months Ended June 30, 2020		Twelve Months Ended December 31, 2019

Asset retirement obligations, beginning of year	$	659	$	609
Fair value of liabilities acquired through Merger	1,062		—
Liabilities incurred	6		35
Liabilities settled	—		(2)
Accretion expense	22		32
Changes in estimated cash flows	—		(15)

Asset retirement obligations, end of period	$	1,749	$	659

Classified on the balance sheet as:


Other long-term liabilities	$	1,749	$	659