Accumulated Other Comprehensive Income (Loss) (Components of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Before-Tax
Net change	$ (19,374)	$ 13,836	$ (39,282)	$ 21,090
Tax Effect
Net change	3,711	(4,499)	11,605	(7,125)
Net-of-Tax
Other comprehensive (loss) income	(15,663)	9,337	(27,677)	13,965
Available- for-Sale Investment Securities
Before-Tax
Net unrealized (losses) gains arising during the period	(12,342)	13,420	(36,919)	22,141
Net realized gains reclassified into net income	(210)	(2,720)	(2,339)	(5,194)
Net change	(12,552)	10,700	(39,258)	16,947
Tax Effect
Net unrealized (losses) gains arising during the period	3,649	(5,643)	10,915	(9,309)
Net realized gains reclassified into net income	62	1,144	690	2,184
Net change	3,711	(4,499)	11,605	(7,125)
Net-of-Tax
Net unrealized (losses) gains arising during the period	(8,693)	7,777	(26,004)	12,832
Net realized gains reclassified into net income	(148)	(1,576)	(1,649)	(3,010)
Other comprehensive (loss) income	(8,841)	6,201	(27,653)	9,822
Foreign Currency Translation Adjustments
Before-Tax
Net unrealized (losses) gains arising during the period	(6,822)	3,136	(24)	4,143
Net change	(6,822)	3,136	(24)	4,143
Tax Effect
Net unrealized (losses) gains arising during the period	0	0	0	0
Net change	0	0	0	0
Net-of-Tax
Net unrealized (losses) gains arising during the period	(6,822)	3,136	(24)	4,143
Net realized gains reclassified into net income	0	0	0	0
Other comprehensive (loss) income	$ (6,822)	$ 3,136	$ (24)	$ 4,143