Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Assets and liabilities measured at fair value on a recurring basis
Marketable securities in deferred compensation plan	$ 2,279	$ 3,060
Fair value measurement on a recurring basis | Deferred compensation plan | Trustees and Management
Assets and liabilities measured at fair value on a recurring basis
Maximum percentage of participants' compensation which is deferrable (as a percent)	100.00%
Marketable securities in deferred compensation plan	$ 2,300