Recently Adopted and Recently Issued Accounting Standards (Details 4) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Defined benefit pension income (expense)	$ (904)	$ 675	$ (1,743)	$ 1,374
Cumulative Effect of New Accounting Principle in Period of Adoption					$ (2,374)		$ (397)
Stranded Income Tax Effects in Accumulated Other Comprehensive Income						$ 21,000
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ (100)		$ (100)		$ (3,894)		$ 709