Revolving Credit Facility (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Facility A Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 15.0
Line of credit facility, unused capacity, commitment fee percentage	0.25%
Line of credit facility, amount outstanding	$ 0.0
Facility A Revolving Credit Sub-Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 5.0
Line of credit facility, unused capacity, commitment fee percentage	1.00%
Facility B Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 30.0
Line of credit facility, unused capacity, commitment fee percentage	0.25%
Line of credit facility, amount outstanding	$ 30.0
London Interbank Offered Rate (LIBOR) [Member] | Facility A Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, interest rate during period	2.50%
London Interbank Offered Rate (LIBOR) [Member] | Facility B Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, unused capacity, commitment fee percentage	3.00%