Recently Adopted and Recently Issued Accounting Standards (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
Adoption of new accounting standard (See Note 2)		397	$ 2,387
Income tax expense	$ 8,266	6,253
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of new accounting standard (See Note 2)		$ (709)	$ 3,907