Operations and Summary of Significant Accounting Policies Recently Adopted Accounting Standards (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncement, Early Adoption [Line Items]
Retained earnings		$ 628,207	$ 676,644
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Retained earnings		$ 400
Accounting Standards Update 2016-02 [Member] | Subsequent Event | Minimum
New Accounting Pronouncement, Early Adoption [Line Items]
Operating Lease, Right-of-Use Asset	$ 36,000
Operating Lease, Liability	35,000
Accounting Standards Update 2016-02 [Member] | Subsequent Event | Maximum
New Accounting Pronouncement, Early Adoption [Line Items]
Operating Lease, Right-of-Use Asset	37,000
Operating Lease, Liability	$ 36,000