Derivatives (Gains (Losses) in Foreign Currency Translation Adjustment and Letters of Credit Fees and Foreign Exchange Income) (Details) - Derivative instruments designated as hedging instruments - Net investment hedges - Foreign exchange swap contracts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in AOCI	$ 6,072	$ (648)	$ 2,908
Gains (losses) recognized in Letters of credit fees and foreign exchange income	$ 0	$ (1,953)	$ 1,124