Stock Benefit Plans - Aspects of Awards Exercised (Details) - Long Term Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Options
Stock Benefit Plans
Weighted average grant date fair value of options granted	$ 4.85	$ 6.38	$ 8.01
Total intrinsic value of options exercised	$ 1,275	$ 7,130	$ 31,822
Total fair value of options that have vested	7,369	10,253	8,446
Total cash received from the exercise of stock options	2,235	$ 17,495	$ 41,658
Compensation cost not yet recognized	$ 5,600
Period for recognition	2 years 5 months 4 days
Stock, Restricted Stock and Restricted Stock Units
Stock Benefit Plans
Weighted average grant date fair value of stock awards granted (in dollars per share)	$ 18.86	$ 48.29	$ 63.80
Total grant date fair value of stock awards granted	$ 29,597	$ 3,007	$ 4,185
Total fair value of stock awards that have vested	2,011	$ 1,027	$ 3,888
Compensation cost not yet recognized	$ 17,600
Period for recognition	2 years 4 months 9 days

The aggregate fair value of stock awards granted at the grant date.

No definition available.

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Represents the aggregate fair value for outstanding stock options that vested during the period.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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-Publisher FASB
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Weighted-average period over which cost not yet recognized is expected to be recognized for 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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Amount of cash inflow from exercise of option under share-based payment arrangement.

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into 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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