Derivatives - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Derivative [Line Items]
OTC Option Asset	$ 2.0	$ 8.9
OTC Option Liability	6.0	3.7
Derivative with Credit Risk Feature, Net	4.6	1.8
Derivative Instruments with Credit-Risk-Related Contingent Features [Member]
Derivative [Line Items]
Derivative, Collateral, Right to Reclaim Cash	71.6	$ 62.6
Derivative, Collateral, Obligation to Return Cash	$ 3.9