Securities (Summary of Pooled Trust Preferred Securities) (Details) (USD $) | Jun. 30, 2014 | Dec. 31, 2013 |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | $1,445,646,000 | $831,819,000 |
Fair Value | 1,484,223,000 | 839,064,000 |
Current deferrals and defaults, assumed recoveries range, low | 1.20% | ' |
Assumed recoveries range, high | 65.50% | ' |
Expected deferrals and defaults, assumed recoveries range, low | 0.00% | ' |
Expected deferrals and defaults, assumed recoveries range, high | 23.70% | ' |
Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 31,652,700 | ' |
Fair Value | 61,856,300 | ' |
Unrealized Gains (Losses) | 30,203,600 | ' |
Moody's, Caa1 Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pref Pretsl IX | Moody's, Caa1 Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 405,300 | ' |
Fair Value | 690,200 | ' |
Unrealized Gains (Losses) | 284,900 | ' |
Number of Issuers Currently Performing | 29 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 23.60% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 10.40% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl XXVI | Moody's, C Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 496,500 | ' |
Fair Value | 960,900 | ' |
Unrealized Gains (Losses) | 464,300 | ' |
Number of Issuers Currently Performing | 51 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 24.10% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 14.90% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl XXV | Moody's, C Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 415,300 | ' |
Fair Value | 843,200 | ' |
Unrealized Gains (Losses) | 427,800 | ' |
Number of Issuers Currently Performing | 51 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 25.70% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 12.60% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl XXI | Moody's, C Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 888,700 | ' |
Fair Value | 2,760,700 | ' |
Unrealized Gains (Losses) | 1,872,000 | ' |
Number of Issuers Currently Performing | 53 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 19.00% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 12.50% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl XX | Moody's, C Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 383,500 | ' |
Fair Value | 651,700 | ' |
Unrealized Gains (Losses) | 268,200 | ' |
Number of Issuers Currently Performing | 46 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 16.80% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 16.20% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl XIX | Moody's, C Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 693,800 | ' |
Fair Value | 1,233,100 | ' |
Unrealized Gains (Losses) | 539,300 | ' |
Number of Issuers Currently Performing | 52 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 10.60% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 12.10% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl XVIII | Moody's, Ca Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 1,586,300 | ' |
Fair Value | 2,796,700 | ' |
Unrealized Gains (Losses) | 1,210,400 | ' |
Number of Issuers Currently Performing | 56 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 21.40% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 9.60% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl XVII | Moody's, C Rating | Fitch, CC Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 708,200 | ' |
Fair Value | 1,439,800 | ' |
Unrealized Gains (Losses) | 731,700 | ' |
Number of Issuers Currently Performing | 37 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 19.00% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 16.50% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl XV | Moody's, C Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 924,400 | ' |
Fair Value | 2,127,900 | ' |
Unrealized Gains (Losses) | 1,203,600 | ' |
Number of Issuers Currently Performing | 57 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 11.60% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 13.70% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl VII | Moody's, Ca Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 372,500 | ' |
Fair Value | 1,721,300 | ' |
Unrealized Gains (Losses) | 1,348,800 | ' |
Number of Issuers Currently Performing | 12 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 47.80% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 11.20% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl V | Moody's, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 16,800 | ' |
Fair Value | 16,200 | ' |
Unrealized Gains (Losses) | -600 | ' |
Number of Issuers Currently Performing | 0 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 65.50% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 0.00% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl IV | Moody's, B1 Rating | Fitch, B Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 145,100 | ' |
Fair Value | 215,700 | ' |
Unrealized Gains (Losses) | 70,600 | ' |
Number of Issuers Currently Performing | 6 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 18.10% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 7.90% | ' |
Excess Subordination as a % of Performing Collateral (3) | 19.00% | ' |
Pretsl XXIV | Moody's, C Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 667,800 | ' |
Fair Value | 811,400 | ' |
Unrealized Gains (Losses) | 143,600 | ' |
Number of Issuers Currently Performing | 63 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 26.10% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 14.40% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl XXIV | Moody's, A3 Rating | Fitch, BBB Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 1,903,700 | ' |
Fair Value | 4,428,200 | ' |
Unrealized Gains (Losses) | 2,524,500 | ' |
Number of Issuers Currently Performing | 63 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 26.10% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 14.40% | ' |
Excess Subordination as a % of Performing Collateral (3) | 24.90% | ' |
Pretsl XXII | Moody's, A1 Rating | Fitch, A Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 549,500 | ' |
Fair Value | 1,490,700 | ' |
Unrealized Gains (Losses) | 941,200 | ' |
Number of Issuers Currently Performing | 71 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 19.50% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 12.60% | ' |
Excess Subordination as a % of Performing Collateral (3) | 31.40% | ' |
Pretsl XXII | Moody's, A1 Rating | Fitch, BBB Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 695,300 | ' |
Fair Value | 2,112,800 | ' |
Unrealized Gains (Losses) | 1,417,500 | ' |
Number of Issuers Currently Performing | 95 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 21.10% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 11.40% | ' |
Excess Subordination as a % of Performing Collateral (3) | 18.30% | ' |
Trapeza XIII | Moody's, Ca Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 1,852,300 | ' |
Fair Value | 3,599,000 | ' |
Unrealized Gains (Losses) | 1,746,700 | ' |
Number of Issuers Currently Performing | 47 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 18.40% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 10.90% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Trapeza XII | Moody's, C Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 1,720,900 | ' |
Fair Value | 2,872,700 | ' |
Unrealized Gains (Losses) | 1,151,800 | ' |
Number of Issuers Currently Performing | 34 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 23.80% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 11.60% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
US Cap III | Moody's, Ca Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 1,802,200 | ' |
Fair Value | 2,566,200 | ' |
Unrealized Gains (Losses) | 764,000 | ' |
Number of Issuers Currently Performing | 29 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 16.00% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 12.70% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
US Cap II | Moody's, Caa1 Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 1,385,000 | ' |
Fair Value | 2,986,500 | ' |
Unrealized Gains (Losses) | 1,601,500 | ' |
Number of Issuers Currently Performing | 36 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 14.90% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 8.50% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
U S Cap I, B1 Class | Moody's, Caa1 Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 2,653,600 | ' |
Fair Value | 5,777,100 | ' |
Unrealized Gains (Losses) | 3,123,500 | ' |
Number of Issuers Currently Performing | 30 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 10.50% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 8.50% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
U S Cap I, B2 Class | Moody's, Caa1 Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 890,600 | ' |
Fair Value | 1,925,700 | ' |
Unrealized Gains (Losses) | 1,035,100 | ' |
Number of Issuers Currently Performing | 30 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 10.50% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 8.50% | ' |
Tpref II | Moody's, Caa3 Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 4,050,100 | ' |
Fair Value | 5,100,000 | ' |
Unrealized Gains (Losses) | 1,049,900 | ' |
Number of Issuers Currently Performing | 17 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 33.90% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 12.30% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Tpref I | Moody's, Ca Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 1,509,300 | ' |
Fair Value | 1,848,500 | ' |
Unrealized Gains (Losses) | 339,200 | ' |
Number of Issuers Currently Performing | 7 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 51.90% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 9.30% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
MMCaps XIX | Moody's, C Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 530,300 | ' |
Fair Value | 76,000 | ' |
Unrealized Gains (Losses) | -454,300 | ' |
Number of Issuers Currently Performing | 32 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 25.40% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 13.80% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
MMCaps XVII | Moody's, Ca Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 1,586,300 | ' |
Fair Value | 2,126,600 | ' |
Unrealized Gains (Losses) | 540,300 | ' |
Number of Issuers Currently Performing | 32 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 13.00% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 8.50% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
MM Comm III | Moody's, B1 Rating | Fitch, BB Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 126,700 | ' |
Fair Value | 3,193,300 | ' |
Unrealized Gains (Losses) | 3,066,600 | ' |
Number of Issuers Currently Performing | 5 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 30.00% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 8.70% | ' |
Excess Subordination as a % of Performing Collateral (3) | 12.80% | ' |
Alesco PF VI | Moody's, Ca Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 679,500 | ' |
Fair Value | 1,615,400 | ' |
Unrealized Gains (Losses) | 935,900 | ' |
Number of Issuers Currently Performing | 45 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 7.50% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 12.10% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Alesco PF IV | Moody's, C Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 385,500 | ' |
Fair Value | 664,000 | ' |
Unrealized Gains (Losses) | 278,500 | ' |
Number of Issuers Currently Performing | 38 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 1.20% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 11.20% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Alesco PF III | Moody's, Ca Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 310,700 | ' |
Fair Value | 677,400 | ' |
Unrealized Gains (Losses) | 366,700 | ' |
Number of Issuers Currently Performing | 31 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 11.10% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 9.20% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Alesco PF III, B1 Class | Moody's, Ca Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 776,400 | ' |
Fair Value | 1,693,500 | ' |
Unrealized Gains (Losses) | 917,100 | ' |
Number of Issuers Currently Performing | 31 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 11.10% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 9.20% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Alesco PF II | Moody's, Ca Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 315,800 | ' |
Fair Value | 459,600 | ' |
Unrealized Gains (Losses) | 143,800 | ' |
Number of Issuers Currently Performing | 30 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 11.80% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 8.90% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |
Pretsl X | Moody's, Caa3 Rating | Fitch, C Rating | Corporate Debt Securities | ' | ' |
Schedule of Held-to-maturity Securities [Line Items] | ' | ' |
Book Value | 224,800 | ' |
Fair Value | 374,300 | ' |
Unrealized Gains (Losses) | $149,500 | ' |
Number of Issuers Currently Performing | 34 | ' |
Current Deferrals and Defaults as a % of Total Collateral (1) | 30.30% | ' |
Expected Deferrals and Defaults as % of Remaining Collateral (2) | 10.20% | ' |
Excess Subordination as a % of Performing Collateral (3) | 0.00% | ' |