Basis of Presentation and Significant Accounting Policies New Accounting Pronouncements (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating Leased Assets [Line Items]
Operating lease right-of-use assets	$ 60,149	$ 60,600	$ 0
Accrued liabilities and other	12,659	12,000
Operating lease liabilities	49,632	50,700	$ 0
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 2,843
Accounting Standards Update 2016-02
Operating Leased Assets [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 2,800