Subsequent Event (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Feb. 01, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Subsequent Event [Line Items]
Sales of common equity securities		$ 461.4	$ 609.8	$ 435.0
Common shares, par value per share (in dollars per share)		$ 1.00	$ 1.00
Symetra
Subsequent Event [Line Items]
Sales of common equity securities	$ 658.0
Common shares, par value per share (in dollars per share)	$ 32.00