Nature of Operations and Basis of Consolidation Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash, Cash Equivalents, and Restricted Cash [Abstract]
Cash and Cash Equivalents	$ 12,433	$ 4,742	$ 8,473	$ 5,079	$ 11,980
Restricted cash	4,852	6,158	3,556	4,426	6,634
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	17,285	$ 10,900	$ 12,029	$ 9,505	$ 18,614
Increase in Restricted Cash	$ 400