Stock-Based Compensation - Stock Option Assumptions and Methodology (Details) - $ / shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2018
Monte Carlo simulation
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Expected dividend yield, Monte Carlo simulation	0.00%
Risk-free interest rate, Monte Carlo simulation	1.56%
Expected volatility rate, Monte Carlo simulation	28.57%
Expected term, Monte Carlo simulation	2 years 11 months 12 days
Grant date fair value, Monte Carlo simulation	24.11
Stock Option \| Black-Sholes option pricing model
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Expected term (in years)		5 years 9 months
Expected volatility		26.38%
Risk-free interest rate		2.86%
Expected dividend yield		0.00%
Weighted average grant date fair value of options granted (usd per share)		$ 5.47

Performance Stock Unit, Fair Value Assumptions, Expected Dividend Rate

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Performance Stock Unit, Fair Value Assumptions, Risk Free Interest Rate

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Performance Stock Units, Grants In Period, Weighted Average Grant Date Fair Value

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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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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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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