Investment Securities (Non-agency securities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	$ 54.0
Super Senior | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	24.9	[1]
Senior | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	29.1	[2]
Subordinate | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	0	[3]
Fair Value | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	54.0		51.5
Fair Value | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	169.2		155.0
Fair Value | Commercial Mortgage Backed Securities Floating Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	41.3
Fair Value | Commercial Mortgage Backed Securities Fixed Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	127.9
Fair Value | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	223.2		206.5
Fair Value | Super Senior | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	87.7	[4]
Fair Value | Super Senior | Commercial Mortgage Backed Securities Floating Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	1.3	[4]
Fair Value | Super Senior | Commercial Mortgage Backed Securities Fixed Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	86.4	[4]
Fair Value | Senior | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	47.6	[2]
Fair Value | Senior | Commercial Mortgage Backed Securities Floating Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	15.0	[2]
Fair Value | Senior | Commercial Mortgage Backed Securities Fixed Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	32.6	[2]
Fair Value | Subordinate | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	33.9	[3]
Fair Value | Subordinate | Commercial Mortgage Backed Securities Floating Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	25.0	[3]
Fair Value | Subordinate | Commercial Mortgage Backed Securities Fixed Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	8.9	[3]
Securities Issued in 2004 | Fair Value | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	6.5
Securities Issued in 2004 | Fair Value | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	0
Securities Issued in 2004 | Fair Value | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	6.5
Securities Issued in 2005 | Fair Value | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	5.7
Securities Issued in 2005 | Fair Value | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	0
Securities Issued in 2005 | Fair Value | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	5.7
Securities Issued in 2006 | Fair Value | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	5.5
Securities Issued in 2006 | Fair Value | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	0
Securities Issued in 2006 | Fair Value | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	5.5
Securities issued in 2007 | Fair Value | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	0
Securities issued in 2007 | Fair Value | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	1.3
Securities issued in 2007 | Fair Value | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	1.3
Securities Issued in 2008 | Fair Value | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	6.5
Securities Issued in 2008 | Fair Value | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	15.0
Securities Issued in 2008 | Fair Value | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	21.5
Securities Issued in 2009 [Member] | Fair Value | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	0
Securities Issued in 2009 [Member] | Fair Value | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	0
Securities Issued in 2009 [Member] | Fair Value | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	0
Securities issued in 2010 | Fair Value | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	6.4
Securities issued in 2010 | Fair Value | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	7.2
Securities issued in 2010 | Fair Value | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	13.6
Securities issued in 2011 | Fair Value | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	0
Securities issued in 2011 | Fair Value | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	13.1
Securities issued in 2011 | Fair Value | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	13.1
Securities issued in 2012 | Fair Value | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	0
Securities issued in 2012 | Fair Value | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	86.3
Securities issued in 2012 | Fair Value | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	86.3
Securities Issued in 2013 | Fair Value | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	17.4
Securities Issued in 2013 | Fair Value | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	38.8
Securities Issued in 2013 | Fair Value | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	56.2
Securities Issued in 2014 [Member] | Fair Value | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	6.0
Securities Issued in 2014 [Member] | Fair Value | Commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	7.5
Securities Issued in 2014 [Member] | Fair Value | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	13.5
Residential, Prime, Financing Receivable [Member] | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	47.6
Residential, Prime, Financing Receivable [Member] | Super Senior | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	24.9	[1]
Residential, Prime, Financing Receivable [Member] | Senior | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	22.7	[2]
Residential, Prime, Financing Receivable [Member] | Subordinate | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	0	[3]
Residential, Subprime, Financing Receivable [Member] | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	6.4
Residential, Subprime, Financing Receivable [Member] | Super Senior | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	0	[1]
Residential, Subprime, Financing Receivable [Member] | Senior | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	6.4	[2]
Residential, Subprime, Financing Receivable [Member] | Subordinate | Non-agency RMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	$ 0	[3]

[1] At issuance, Super Senior, or in the case of resecuritization, the underlying securities, were rated AAA by Standard & Poor's, Aaa by Moody's, or AAA by Fitch Ratings ("Fitch") and were senior to other AAA or Aaa bonds.

[2] At issuance, Senior, or in the case of resecuritization, the underlying securities, were rated AAA by Standard & Poor's, Aaa by Moody's, or AAA by Fitch and were senior to non-AAA or non-Aaa bonds.

[3] At issuance, Subordinate were not rated AAA by Standard & Poor's, Aaa by Moody's, or AAA by Fitch and were junior to other bonds.

[4] At issuance, Super Senior, or in the case of resecuritization, the underlying securities, were rated AAA by Standard & Poor's, Aaa by Moody's or AAA by Fitch and were senior to other AAA or Aaa bonds.