CONSOLIDATED STATEMENTS OF CASH FLOWS - (Restricted cash and investments) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Restricted cash and investments
Cash and cash equivalents at beginning of period	$ 27,042	$ 10,309	$ 7,015
Restricted cash at beginning of period	1,757	1,712	1,707
Cash and cash equivalents and Restricted cash at beginning of period	28,799	12,021	8,722
Cash and cash equivalents at end of period	44,251	27,042	10,309
Restricted cash at end of period	1,666	1,757	1,712
Cash and cash equivalents and Restricted cash at end of period	$ 45,917	$ 28,799	$ 12,021