Employee Benefit Plan (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan Disclosure [Line Items]
Value of contributed shares	$ 3,037	$ 2,978	$ 2,960
Domestic Plan [Member] | GP Retirement Savings Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Discretionary contribution shares	337,371	219,427	162,572
Value of contributed shares	$ 3,000	$ 3,000	$ 3,000
Foreign Plan [Member] | Defined Contribution Pension Schemes [Member]
Defined Contribution Plan Disclosure [Line Items]
Contributed cash	$ 2,800	$ 2,700	$ 2,700