Other Assets (Schedule of Other Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Equity Method Investments And Other Assets [Abstract]
Accounts receivable and other assets	$ 6,249	$ 9,017
Regulatory deposits	8,208	8,208
Reserves for replacement, insurance and tax escrows	4,141	4,046
Marketable securities	0	11,745
Other Assets	$ 18,598	$ 33,016