Commitments and Contingencies - Assets Sold with Recourse (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) loan	Dec. 31, 2015 USD ($)	Sep. 12, 2014 USD ($)	Jul. 31, 2014 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans repurchased | loan	0
Principal balance of loans sold in secondary market	$ 312.3	$ 344.2
Non-performing residential mortgage loans | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of loans sold			$ 4.0	$ 173.7