Accumulated Other Comprehensive Income (Loss) (Components of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Before-Tax
Net change, other comprehensive income (loss)	$ 15,224	$ (24,115)	$ 87,876	$ (63,397)
Tax Effect
Net change, other comprehensive income (loss)	(6,219)	5,746	(30,669)	17,351
Net-of-Tax
Other comprehensive income (loss)	9,005	(18,369)	57,207	(46,046)
Available- for-Sale Investment Securities
Before-Tax
Net unrealized gains (losses) arising during the period	16,900	(19,319)	92,369	(56,238)
Net realized gains reclassified into net income	(58)	(35)	(3,066)	(2,374)
Net change, other comprehensive income (loss)	16,842	(19,354)	89,303	(58,612)
Tax Effect
Net unrealized gains (losses) arising during the period	(4,996)	5,735	(27,308)	16,650
Net realized gains reclassified into net income	17	11	906	701
Net change, other comprehensive income (loss)	(4,979)	5,746	(26,402)	17,351
Net-of-Tax
Net unrealized gains (losses) arising during the period	11,904	(13,584)	65,061	(39,588)
Net realized gains reclassified into net income	(41)	(24)	(2,160)	(1,673)
Other comprehensive income (loss)	11,863	(13,608)	62,901	(41,261)
Foreign Currency Translation Adjustments, Net of Hedges
Before-Tax
Net unrealized gains (losses) arising during the period	(1,618)	(4,761)	(1,427)	(4,785)
Net change, other comprehensive income (loss)	(1,618)	(4,761)	(1,427)	(4,785)
Tax Effect
Net unrealized gains (losses) arising during the period	(1,240)	0	(4,267)	0
Net change, other comprehensive income (loss)	(1,240)	0	(4,267)	0
Net-of-Tax
Net unrealized gains (losses) arising during the period	(2,858)	(4,761)	(5,694)	(4,785)
Net realized gains reclassified into net income	0	0	0	0
Other comprehensive income (loss)	$ (2,858)	$ (4,761)	$ (5,694)	$ (4,785)