Equity Compensation Plans - Stock-Based Compensation Expense (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based compensation expense	$ 19,919	$ 19,358	$ 21,049
Total compensation cost related to unvested awards not yet recognized	$ 28,600
Stock based compensation expense period	2 years 2 months 12 days
Deferred income tax benefit related to stock-based compensation expense	$ 4,300	4,400	7,100
Income tax benefit realized for the tax deductions from stock-based compensation	$ 3,900	$ 5,300	$ 11,000

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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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