Investments Other investment disclosures (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Cost-method Investments [Line Items]
Amortization Method Qualified Affordable Housing Project Investments	$ 34.2	$ 27.7
Qualified Affordable Housing Project Investments, Commitment	11.3	7.8
Income Tax Expense [Member]
Schedule of Cost-method Investments [Line Items]
Amortization Method Qualified Affordable Housing Project Investments, Amortization	1.6	1.3	$ 1.0
Affordable Housing Tax Credits and Other Tax Benefits, Amount	$ 1.7	$ 1.3	$ 1.1