Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Summary of financial assets measured at fair value on a recurring basis

The following table summarizes the Company’s assets at fair value on a recurring basis at December 31, 2017 and 2016 by level within the fair value hierarchy. There were no liabilities measure at fair value on a recurring basis at December 31, 2017 and 2016. These assets are classified in their entirety based on the lowest level of input that is significant to the fair value measurement (in thousands):



	At December 31, 2017								At December 31, 2016
							Total Fair								Total Fair
	Level 1		Level 2		Level 3		Value		Level 1		Level 2		Level 3		Value
Assets:
Cash equivalents	$	195,584	$	—	$	—	$	195,584	$	107,721	$	—	$	—	$	107,721
Total Assets	$	195,584	$	—	$	—	$	195,584	$	107,721	$	—	$	—	$	107,721

Summary of changes in the allowance for doubtful accounts and sales allowances

The following table summarizes the changes in the allowance for doubtful accounts and sales allowances (in thousands):



	Year Ended December 31,
	2017			2016			2015
Allowances, at beginning of period	$	2,600		$	2,720		$	2,069
Charged as a reduction of revenue	7,734			7,042			6,716
Charged to bad debt expense in general and administrative expenses	1,385			1,285			925
Write-offs, net of recoveries	(8,689		)	(8,447		)	(6,990		)
Allowances, at end of period	$	3,030		$	2,600		$	2,720

Schedule of expected amortization expense with respect to capitalized software costs

Expected amortization expense with respect to capitalized software costs at December 31, 2017 for each of the five years through December 31, 2022 is as follows (in thousands):



Years ended December 31,
2018	$	11,529
2019	6,822
2020	3,849
2021	103
2022	50
Total amortization expense	$	22,353