Recently Adopted and Recently Issued Accounting Standards - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Defined benefit pension income (expense)	$ (928)	$ 680	$ (2,671)	$ 2,054
Adoption of new accounting standard (See Note 2)					$ 2,375		$ 397
Stranded income tax effects in accumulated other comprehensive income						$ 21,000
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of new accounting standard (See Note 2)	$ 100		$ 100		$ 3,895		$ (709)