Recently Adopted and Recently Issued Accounting Standards Recently Adopted and Recently Issued Accounting Standards (Details 4) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Defined benefit pension income (expense)	$ (839)	$ 699
Cumulative Effect of New Accounting Principle in Period of Adoption		$ (397)	$ (2,387)
Stranded Income Tax Effects in Accumulated Other Comprehensive Income			$ 21,000
intra-entity asset transfer [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ (100)