Common Stock (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Aug. 06, 2015
Equity [Abstract]
Share repurchase program, authorized amount			$ 100.0
Treasury stock at cost (in shares)	345,000	119,000
Treasury stock acquired (in shares)	226,170	118,772
Cost of common shares repurchased	$ 9.4	$ 5.0
Share repurchase, average price per share	$ 41.43	$ 42.13
Remaining authorized repurchase amount	$ 85.6