Investments (Narrative) (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Gain (Loss) on Investments [Line Items]
Securities held-to-maturity with unrealized losses	$ 0	$ 0
Other-than-temporary impairments, available-for-sale securities	0	0
Single Largest Loss Position	294,000	340,000
Second Largest Loss Position	52,000	85,000
Third Largest Loss Position	$ 42,000	$ 66,000
Maximum
Gain (Loss) on Investments [Line Items]
Percent of investment portfolio below investment grade	6.53%