Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies [Abstract]
Line of credit facility, commitment amount	$ 67,000	$ 73,500
Letters of credit outstanding, amount	17,700	21,400
Amounts available under lines of credit	$ 135,300	$ 128,800