Accumulated Other Comprehensive Income (Loss) (Components of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Before-Tax
Net change	$ 32,557	$ (19,908)
Tax Effect
Net change	(7,366)	7,894
Net-of-Tax
Other comprehensive income (loss)	25,191	(12,014)
Available- for-Sale Investment Securities
Before-Tax
Net unrealized (losses) gains arising during the period	30,938	(24,577)
Net realized gains reclassified into net income	(1,561)	(2,129)
Net change	29,377	(26,706)
Tax Effect
Net unrealized (losses) gains arising during the period	(7,827)	7,266
Net realized gains reclassified into net income	461	628
Net change	(7,366)	7,894
Net-of-Tax
Net unrealized (losses) gains arising during the period	23,111	(17,311)
Net realized gains reclassified into net income	(1,100)	(1,501)
Other comprehensive income (loss)	22,011	(18,812)
Foreign Currency Translation Adjustments
Before-Tax
Net unrealized (losses) gains arising during the period	3,180	6,798
Net change	3,180	6,798
Tax Effect
Net unrealized (losses) gains arising during the period	0	0
Net change	0	0
Net-of-Tax
Net unrealized (losses) gains arising during the period	3,180	6,798
Net realized gains reclassified into net income	0	0
Other comprehensive income (loss)	$ 3,180	$ 6,798