Accumulated Other Comprehensive Income (Loss) (Components of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Before-Tax
Net change	$ (24,115)	$ 582	$ (63,397)	$ 21,672
Tax Effect
Net change	5,746	1,382	17,351	(5,743)
Net-of-Tax
Other comprehensive (loss) income	(18,369)	1,964	(46,046)	15,929
Available- for-Sale Investment Securities
Before-Tax
Net unrealized (losses) gains arising during the period	(19,319)		(56,238)
Net realized gains reclassified into net income	(35)		(2,374)
Net change	(19,354)		(58,612)
Tax Effect
Net unrealized (losses) gains arising during the period	5,735		16,650
Net realized gains reclassified into net income	11		701
Net change	5,746		17,351
Net-of-Tax
Net unrealized (losses) gains arising during the period	(13,584)		(39,588)
Net realized gains reclassified into net income	(24)		(1,673)
Other comprehensive (loss) income	(13,608)		(41,261)
Available- for-Sale Investment Securities
Before-Tax
Net unrealized (losses) gains arising during the period		(1,749)		20,392
Net realized gains reclassified into net income		(1,539)		(6,733)
Net change		(3,288)		13,659
Tax Effect
Net unrealized (losses) gains arising during the period		735		(8,574)
Net realized gains reclassified into net income		647		2,831
Net change		1,382		(5,743)
Net-of-Tax
Net unrealized (losses) gains arising during the period		(1,014)		11,818
Net realized gains reclassified into net income		(892)		(3,902)
Other comprehensive (loss) income		(1,906)		7,916
Foreign Currency Translation Adjustments
Before-Tax
Net unrealized (losses) gains arising during the period	(4,761)	3,870	(4,785)	8,013
Net change	(4,761)	3,870	(4,785)	8,013
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	(4,761)	3,870	(4,785)	8,013
Net realized gains reclassified into net income	0	0	0	0
Other comprehensive (loss) income	$ (4,761)	$ 3,870	$ (4,785)	$ 8,013

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