Debt (Short-term Borrowings) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Maximum amount borrowed	$ 555,000	$ 367,000	$ 412,000
Weighted average interest rate	3.32%	2.56%	1.94%