Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use assets	$ 71,965	$ 69,096	$ 0
Operating Lease, Liability	$ 78,011	$ 75,200