Contract Balances

12 Months Ended

Dec. 31, 2021

Revenue Recognition and Deferred Revenue [Abstract]

Contract Balances

Contract Balances

Contract assets were $77.9 million and $20.8 million as of December 31, 2021 and December 31, 2020, respectively.

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

	Year Ended December 31,
	2021		2020		2019
Allowance for doubtful accounts:
Balance, beginning of period	$	3,427	$	4,522	$	4,838
Additions charged to expense	1,073		2,650		2,772
Less: write-offs, net of recoveries and other adjustments	(742)		(3,745)		(3,088)
Balance, end of period	$	3,758	$	3,427	$	4,522

For the years ended December 31, 2021 and 2020, we recognized revenue of $48.4 million and $37.1 million, respectively, that was included in the deferred revenue balance at the beginning of the related period.

Contract Cost Assets

As of December 31, 2021 and 2020, we had $35.5 million and $50.7 million, respectively, of contract cost assets. For the years ended December 31, 2021 and 2020, we did not record any material impairment losses to our contract cost assets.

We recorded amortization expense related to contract cost assets of $41.6 million, $36.5 million and $35.3 million during the years ended December 31, 2021, 2020 and 2019, respectively.