Fair Value Measurements (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Level 1 to Level 2 transfers, assets amount	$ 0	$ 0	$ 0
Level 2 to Level 1 transfers, assets amount	0	0	0
Level 2 to Level 1 transfers, liabilities amount	0	0	0
Assets measured at fair value on recurring basis using significant unobservable inputs	0	0
Measured On A Nonrecurring Basis [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities measured at fair value on nonrecurring basis	$ 0	$ 0	$ 0