Accumulated Other Comprehensive Income (Loss) (Components of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Before - Tax
Other comprehensive income (loss)	$ 9,084	$ (49,620)	$ (26,710)
Tax Effect
Other comprehensive income (loss)	1,543	16,415	7,532
Net-of- Tax
Net unrealized gains (losses) arising during the period	15,284	(27,200)	4,215
Net realized gains reclassified into net income	(4,657)	(6,005)	(23,393)
Other comprehensive income (loss)	10,627	(33,205)	(19,178)
Available- for-Sale Investment Securities
Before - Tax
Net unrealized gains (losses) arising during the period	4,368	(28,681)	22,454
Net realized gains reclassified into net income	(8,037)	(10,362)	(40,367)
Other comprehensive income (loss)	(3,669)	(39,043)	(17,913)
Tax Effect
Net unrealized gains (losses) arising during the period	(1,837)	12,058	(9,442)
Net realized gains reclassified into net income	3,380	4,357	16,974
Other comprehensive income (loss)	1,543	16,415	7,532
Net-of- Tax
Net unrealized gains (losses) arising during the period	2,531	(16,623)	13,012
Net realized gains reclassified into net income	(4,657)	(6,005)	(23,393)
Other comprehensive income (loss)	(2,126)	(22,628)	(10,381)
Foreign Currency Translation Adjustments
Before - Tax
Net unrealized gains (losses) arising during the period	12,753	(10,577)	(8,797)
Other comprehensive income (loss)	12,753	(10,577)	(8,797)
Tax Effect
Net unrealized gains (losses) arising during the period	0	0	0
Other comprehensive income (loss)	0	0	0
Net-of- Tax
Net unrealized gains (losses) arising during the period	12,753	(10,577)	(8,797)
Net realized gains reclassified into net income	0	0	0
Other comprehensive income (loss)	$ 12,753	$ (10,577)	$ (8,797)