Fair Value Fair Value (Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Minimum [Member] | Trust Preferred Predominantly Banks [Member] | Constant Default Rate Until 2016 [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Assumption for Fair Value of Assets or Liabilities that relate to Transferor's Continuing Involvement, Prepayment Speed
Minimum [Member] | Trust Preferred Predominantly Banks [Member] | Constant Default Rate Year 1 [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Assumption For Fair Value Of Assets Or Liabilities Constant Default Rate	0.30%	0.30%
Minimum [Member] | Trust Preferred Predominantly Banks [Member] | Constant Default Rate Year 2 to 5 [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Assumption For Fair Value Of Assets Or Liabilities Constant Default Rate	0.50%	0.50%
Minimum [Member] | Trust Preferred Predominantly Banks [Member] | Constant Default Rate Year 6 to Maturity [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Assumption For Fair Value Of Assets Or Liabilities Constant Default Rate	0.60%	0.60%
Maximum [Member] | Trust Preferred Predominantly Banks [Member] | Constant Default Rate Until 2016 [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Assumption for Fair Value of Assets or Liabilities that relate to Transferor's Continuing Involvement, Prepayment Speed
Maximum [Member] | Trust Preferred Predominantly Banks [Member] | Constant Default Rate Year 1 [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Assumption For Fair Value Of Assets Or Liabilities Constant Default Rate	0.50%	0.80%
Maximum [Member] | Trust Preferred Predominantly Banks [Member] | Constant Default Rate Year 2 to 5 [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Assumption For Fair Value Of Assets Or Liabilities Constant Default Rate	0.70%	0.90%
Maximum [Member] | Trust Preferred Predominantly Banks [Member] | Constant Default Rate Year 6 to Maturity [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Assumption For Fair Value Of Assets Or Liabilities Constant Default Rate	0.70%	0.70%
Asset-Backed Securities [Member] | Trust Preferred Predominantly Banks [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Assumption for Fair Value of Assets or Liabilities that relate to Transferor's Continuing Involvement, Static Pool Losses	100.00%	100.00%
Level 3 [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Investments, Fair Value Disclosure	445,629	401,957
Level 3 [Member] | Trust Preferred Predominantly Banks [Member] | Asset-Backed Securities [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Investments, Fair Value Disclosure	438,338	393,007
Level 3 [Member] | Other Credit Derivatives [Member] | Asset-Backed Securities [Member]
Summary of Quantitative Information Relating to the Principal Valuation Techniques and Significant Unobservable Inputs for Level 3 [Line Items]
Investments, Fair Value Disclosure	4,826