Accumulated Other Comprehensive Income (Loss) (Components of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Before-Tax
Net change, other comprehensive income (loss)	$ 37,198	$ 32,557
Tax Effect
Net change, other comprehensive income (loss)	(11,909)	(7,366)
Net-of-Tax
Net unrealized gains (losses) arising during the period	26,366	26,291
Net realized gains reclassified into net income	(1,077)	(1,100)
Other comprehensive income	25,289	25,191
Available- for-Sale Investment Securities
Before-Tax
Net unrealized gains arising during the period	40,493	30,938
Net realized gains reclassified into net income	(1,529)	(1,561)
Net change, other comprehensive income (loss)	38,964	29,377
Tax Effect
Net unrealized gains (losses) arising during the period	(11,963)	(7,827)
Net realized gains reclassified into net income	452	461
Net change, other comprehensive income (loss)	(11,511)	(7,366)
Net-of-Tax
Net unrealized gains (losses) arising during the period	28,530	23,111
Net realized gains reclassified into net income	(1,077)	(1,100)
Other comprehensive income	27,453	22,011
Foreign Currency Translation Adjustments, Net of Hedges
Before-Tax
Net unrealized gains arising during the period	(1,766)	3,180
Net change, other comprehensive income (loss)	(1,766)	3,180
Tax Effect
Net unrealized gains (losses) arising during the period	(398)	0
Net change, other comprehensive income (loss)	(398)	0
Net-of-Tax
Net unrealized gains (losses) arising during the period	(2,164)	3,180
Net realized gains reclassified into net income	0	0
Other comprehensive income	$ (2,164)	$ 3,180