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-Publisher FASB
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-Topic 230
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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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Stock-Based Compensation - Employee Stock Purchase Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from shares issued in connection with employee stock purchase plan	$ 0	$ 0	$ 3,660	$ 2,149
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)			6 months	6 months
Risk-free interest rate (as percent)			1.50%	2.60%
Expected volatility (as percent)			40.60%	48.60%
Unrecognized compensation expense	$ 96		$ 96
Unrecognized compensation expense, period for recognition (years)			14 days
Class A Common Stock \| Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued during period (in shares)			94,020
Shares issued during period, weighted average price per share (in dollars per share)			$ 38.93
Proceeds from shares issued in connection with employee stock purchase plan			$ 3,700