Basis of Presentation and Significant Accounting Policies (Basis of Presentation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Basis of Presentation [Line Items]
(Benefit) expense from deferred compensation plan liability	$ (2,480)	$ 6,932	$ 5,213
(Loss) income from deferred compensation plan assets	$ (2,480)	6,932	5,213
General and Administrative Expense
Basis of Presentation [Line Items]
Unincorporated business tax		$ 1,285	$ 694