Accumulated Other Comprehensive Income (Reclassifications out of other comprehensive income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other-than-temporary impairment amount reclassified from accumulated other comprehensive income	$ 0	$ 0	$ 1,490
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Interest Rate Contract	488	3,642	6,443
Tax effect from increase in capital gains tax rate, Cash flow hedges	0	300	(297)
Gain On Sale Of Investments	6,896	12,207	2,572
Other-than-temporary impairment amount reclassified from accumulated other comprehensive income	0	0	1,490
Residual tax effect from OIB's change in applicable tax rate AFS	104	32	45
Tax effect from increase in capital gains tax rate AFS	(284)	(293)	516
Total	$ 7,204	$ 15,888	$ 7,789