Accounting Policies Accounting Policies (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	[1]	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total assets	$ 1,868,404		$ 1,862,866		$ 1,817,574
Liabilities	$ 1,638,931		$ 1,640,324
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total assets		$ 4,400
Liabilities		$ 4,400

[1] Derived from audited consolidated financial statements.