Investments (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($) security	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) security	Sep. 30, 2016 USD ($)	Dec. 31, 2016 security
Gross gains on investments	$ 3,400	$ 1,400	$ 6,400	$ 2,100
Gross losses on investments	200	300	700	500
Proceeds from sale of investment securities	11,400	$ 5,400	19,400	21,300
Other-than-temporary impairments	$ 850		$ 4,257	$ 2,888
Equity Securities [Member]
Number of debt security positions, greater than 12 months | security					1
Debt Securities [Member]
Number of debt security positions, greater than 12 months | security	17		17		28