Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Summary of Property and Equipment Useful Life

Property and equipment, net, are stated at cost, subject to review of impairment, and depreciated using the straight-line method over the estimated useful lives of the assets as follows:



Building		39 years
Computer equipment and software		3-5 years
Furniture and fixtures		3-7 years
Leasehold and other improvements		shorter of the lease term or estimated useful life

Property and equipment, net consists of the following (in thousands):



	December 31,
	2019			2018
Computer equipment	$	680,160		$	493,536
Computer software	59,511			58,303
Leasehold and other improvements	125,299			74,721
Furniture and fixtures	53,651			42,551
Building⁽¹⁾	—			6,551
Construction in progress⁽¹⁾	6,830			10,167
Property and equipment, gross	925,451			685,829
Less: Accumulated depreciation	(457,366		)	(338,613		)
Property and equipment, net	$	468,085		$	347,216

(1)

We adopted Topic 842 using the modified retrospective method as of January 1, 2019 and derecognized $10.6 million in building and construction in progress assets that we were previously deemed to own under the prior lease accounting standards. These assets are recognized under our operating lease right-of-use assets under Topic 842 as of December 31, 2019.

Changes in Allowance for Doubtful Accounts

The following table presents the changes in the allowance for doubtful accounts (in thousands):



	Balance at Beginning of Year		Additions: Charged to Operations	Additions: Charged to Deferred Revenue	Less: Write-offs	Balance at End of Year
Year ended December 31, 2019
Allowance for doubtful accounts	$	4,649	1,284	1,306	1,043	$	6,196
Year ended December 31, 2018
Allowance for doubtful accounts	$	3,115	1,255	1,177	898	$	4,649
Year ended December 31, 2017
Allowance for doubtful accounts	$	2,323	1,688	194	1,090	$	3,115