Income Taxes (Summary of Deferred Income Tax Asset Valuation Allowance) (Details) - Deferred income tax asset valuation allowance - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount, Beginning Balance	$ 95,398	$ 80,796	$ 109,913
Additions (reductions) charged to expense	14,245	14,602	(28,071)
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction	0	0	(1,046)
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount, Ending Balance	$ 109,643	$ 95,398	$ 80,796