Basis of Presentation and Significant Accounting Policies Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accounting Policies [Abstract]
Effective Income Tax Rate Reconciliation, Percent				(12.10%)
Provision (benefit) for income taxes	$ 2,446	$ 54,100	$ 3,317	$ 3,570	$ 3,398