Property and Equipment

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment [Abstract]

Property and equipment consists of the following (in millions):



	December 31,
	2016			2015
Land	$	696		$	596
Buildings	3,109			2,273
Leasehold improvements	531			447
Network equipment	5,179			3,633
Computer software, office equipment and other	398			248
Construction in progress	1,890			622
Total	11,803			7,819
Less: Accumulated depreciation	(3,212		)	(2,132		)
Property and equipment, net	$	8,591		$	5,687

Depreciation expense on property and equipment was $1.59 billion, $1.22 billion, and $923 million during 2016, 2015, and 2014, respectively.

Property and equipment as of December 31, 2016 and 2015 includes $283 million and $287 million, respectively, acquired under capital lease agreements, of which a substantial majority, is included in network equipment. Accumulated depreciation of property and equipment acquired under these capital leases was $30 million and $71 million at December 31, 2016 and 2015, respectively.

Construction in progress includes costs mostly related to construction of data centers, network equipment infrastructure to support our data centers around the world, and office buildings. The construction of office buildings includes leased office spaces for which we are considered to be the owner for accounting purposes. See Note 9 in these notes to the consolidated financial statements for additional information. No interest was capitalized during the years ended December 31, 2016, 2015 and 2014.