Investments (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Investment In Organization [Line Items]
Reclassification of net unrealized losses from accumulated other comprehensive income (AOCI) to retained earnings	$ 0
Minimum [Member]
Investment In Organization [Line Items]
Treasury Bills, term	1 month
Maximum [Member]
Investment In Organization [Line Items]
Treasury Bills, term	7 months
Accounting Standards Update No. 2016-01 [Member]
Investment In Organization [Line Items]
Reclassification of net unrealized losses from accumulated other comprehensive income (AOCI) to retained earnings	$ 7