Goodwill and Other Intangible Assets - Goodwill Acquired (Details) - USD ($) $ in Millions		12 Months Ended
	Sep. 01, 2015	Dec. 31, 2015
Goodwill and Other Intangible Assets
Goodwill from acquisitions		$ 104.8
AXA pension business
Goodwill and Other Intangible Assets
Purchase price of acquired business	$ 335.5
Goodwill from acquisitions	$ 104.8
Distribution agreements | AXA pension business
Goodwill and Other Intangible Assets
Exclusive distribution agreement period	15 years
Finite lived intangible assets acquired	$ 53.0
Finite lived intangible asset, useful life	15 years
Customer relationships | AXA pension business
Goodwill and Other Intangible Assets
Finite lived intangible assets acquired	$ 138.0
Finite lived intangible asset, useful life	30 years