Financial Derivatives (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Written credit derivative spread threshold	20.00%	20.00%
Credit Default Swap, Selling Protection [Member]
Derivative [Line Items]
Credit risk derivative in excess of threshold, at fair value, net	$ (0.2)	$ (1.0)
Total net up-front payments received	$ (3.2)	$ (2.0)
Minimum
Derivative [Line Items]
Spread on written credit derivatives	0.14%	0.218%
Upfront points on written credit derivative in excess of threshold	55.9	56.3
Maximum
Derivative [Line Items]
Spread on written credit derivatives	4.491%	19.56%
Upfront points on written credit derivative in excess of threshold	82.3	74.7