Commitments and Contingencies (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Acquisition of mortgage loans
Loss Contingencies [Line Items]
Amount of purchase commitment	$ 162.6	$ 221.0
Purchase of limited partnerships and private placement investments
Loss Contingencies [Line Items]
Amount of purchase commitment	$ 540.2	$ 330.4