Equity Compensation Plans - Stock-Based Compensation Expense (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based compensation expense	$ 25,237	$ 19,919	$ 19,358
Total compensation cost related to unvested awards not yet recognized	$ 26,800
Stock based compensation expense period	2 years 3 months 18 days
Deferred income tax benefit related to stock-based compensation expense	$ 5,800	4,300	4,400
Income tax benefit realized for the tax deductions from stock-based compensation	$ 4,000	$ 3,900	$ 5,300

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

+ References

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-Publisher FASB
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-Topic 718
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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 tax benefit for recognition of expense of award under share-based payment arrangement.

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Amount of tax benefit from exercise of option under share-based payment arrangement.

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Amount of noncash expense for share-based payment arrangement.

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