Recent Accounting Developments (Narratives) (Details) - USD ($) $ in Thousands		3 Months Ended
	Jan. 01, 2018	Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle
Income Tax Expense (Benefit)		$ (300)
Cumulative effect on other comprehensive income		$ 4,707	$ 1,440
ASU 2017-12
New Accounting Pronouncements or Change in Accounting Principle
Cumulative effect on retained earnings	$ 400
Cumulative effect on other comprehensive income	$ (400)