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Valuation (Fair Value Measurement Using Significant Unobservable Inputs) (Details) (Level 3 [Member], USD $)
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3 Months Ended |
9 Months Ended |
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Sep. 30, 2012
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Sep. 30, 2011
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Sep. 30, 2012
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Sep. 30, 2011
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| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
|
|
|
|
| Assets, Beginning Balance |
$ 461,540,000 |
$ 448,542,000 |
$ 504,861,000 |
$ 443,539,000 |
| Assets, Accreted Discounts/Amortized Premiums |
5,940,000 |
4,144,000 |
14,358,000 |
11,337,000 |
| Assets, Realized Gain/(Loss) |
12,419,000 |
6,157,000 |
14,299,000 |
27,016,000 |
| Assets, Change in Net Unrealized Gain/(Loss) |
19,562,000 |
(17,424,000) |
53,924,000 |
(46,516,000) |
| Assets, Purchases |
150,769,000 |
116,128,000 |
333,200,000 |
331,073,000 |
| Assets, Sales |
(103,172,000) |
(76,662,000) |
(373,584,000) |
(285,564,000) |
| Assets, Transfers In and/or Out of Level 3 |
0 |
0 |
0 |
0 |
| Assets, Ending Balance |
547,058,000 |
480,885,000 |
547,058,000 |
480,885,000 |
| Liabilities, Beginning Balance |
(1,415,000) |
|
0 |
|
| Liabilities, Accreted Discounts/Amortized Premiums |
(15,000) |
|
(44,000) |
|
| Liabilities, Realized Gain/(Loss) |
0 |
|
0 |
|
| Liabilities, Change in Net Unrealized Gain/(Loss) |
(51,000) |
|
(30,000) |
|
| Liabilities, Purchases |
42,000 |
|
157,000 |
|
| Liabilities, Sales |
0 |
|
(1,522,000) |
|
| Liabilities, Transfers In and/or Out of Level 3 |
0 |
|
0 |
|
| Liabilities, Ending Balance |
(1,439,000) |
|
(1,439,000) |
|
| Change in net unrealized gain (loss) on investments |
23,300,000 |
(15,900,000) |
33,700,000 |
(32,200,000) |
| Change in net unrealized gain (loss) in financial derivative assets |
(3,800,000) |
2,300,000 |
(8,100,000) |
(12,600,000) |
| Change in net unrealized gain (loss) in securitized debt |
(50,000) |
|
(30,000) |
|
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Investments [Member]
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|
|
|
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| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
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|
|
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| Assets, Beginning Balance |
422,781,000 |
378,713,000 |
443,363,000 |
340,689,000 |
| Assets, Accreted Discounts/Amortized Premiums |
5,940,000 |
4,144,000 |
14,358,000 |
11,337,000 |
| Assets, Realized Gain/(Loss) |
8,456,000 |
3,069,000 |
15,813,000 |
18,620,000 |
| Assets, Change in Net Unrealized Gain/(Loss) |
23,385,000 |
(17,176,000) |
49,639,000 |
(41,529,000) |
| Assets, Purchases |
150,664,000 |
116,006,000 |
332,870,000 |
330,547,000 |
| Assets, Sales |
(95,628,000) |
(63,777,000) |
(340,445,000) |
(238,685,000) |
| Assets, Transfers In and/or Out of Level 3 |
0 |
0 |
0 |
0 |
| Assets, Ending Balance |
515,598,000 |
420,979,000 |
515,598,000 |
420,979,000 |
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Financial Derivatives - Assets [Member]
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|
|
|
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| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
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|
|
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| Assets, Beginning Balance |
38,759,000 |
69,829,000 |
61,498,000 |
102,850,000 |
| Assets, Accreted Discounts/Amortized Premiums |
0 |
0 |
0 |
0 |
| Assets, Realized Gain/(Loss) |
3,963,000 |
3,088,000 |
(1,514,000) |
8,396,000 |
| Assets, Change in Net Unrealized Gain/(Loss) |
(3,823,000) |
(248,000) |
4,285,000 |
(4,987,000) |
| Assets, Purchases |
105,000 |
122,000 |
330,000 |
526,000 |
| Assets, Sales |
(7,544,000) |
(12,885,000) |
(33,139,000) |
(46,879,000) |
| Assets, Transfers In and/or Out of Level 3 |
0 |
0 |
0 |
0 |
| Assets, Ending Balance |
31,460,000 |
59,906,000 |
31,460,000 |
59,906,000 |
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Securitized Debt [Member]
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|
|
|
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| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
|
|
|
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| Liabilities, Beginning Balance |
(1,415,000) |
|
0 |
|
| Liabilities, Accreted Discounts/Amortized Premiums |
(15,000) |
|
(44,000) |
|
| Liabilities, Realized Gain/(Loss) |
0 |
|
0 |
|
| Liabilities, Change in Net Unrealized Gain/(Loss) |
(51,000) |
|
(30,000) |
|
| Liabilities, Purchases |
42,000 |
|
157,000 |
|
| Liabilities, Sales |
0 |
|
(1,522,000) |
|
| Liabilities, Transfers In and/or Out of Level 3 |
0 |
|
0 |
|
| Liabilities, Ending Balance |
(1,439,000) |
|
(1,439,000) |
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Credit Default Swaps On Asset Backed Securities [Member] | Financial Derivatives - Assets [Member]
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|
|
|
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| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
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|
|
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| Assets, Beginning Balance |
38,759,000 |
69,829,000 |
61,498,000 |
102,850,000 |
| Assets, Accreted Discounts/Amortized Premiums |
0 |
0 |
0 |
0 |
| Assets, Realized Gain/(Loss) |
3,963,000 |
3,088,000 |
(1,514,000) |
8,396,000 |
| Assets, Change in Net Unrealized Gain/(Loss) |
(3,823,000) |
(248,000) |
4,285,000 |
(4,987,000) |
| Assets, Purchases |
105,000 |
122,000 |
330,000 |
526,000 |
| Assets, Sales |
(7,544,000) |
(12,885,000) |
(33,139,000) |
(46,879,000) |
| Assets, Transfers In and/or Out of Level 3 |
0 |
0 |
0 |
0 |
| Assets, Ending Balance |
31,460,000 |
59,906,000 |
31,460,000 |
59,906,000 |
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U.S. Treasury And Agency Residential Mortgage-Backed Securities [Member] | Investments [Member]
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| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
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|
|
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| Assets, Beginning Balance |
4,667,000 |
5,227,000 |
5,337,000 |
0 |
| Assets, Accreted Discounts/Amortized Premiums |
(534,000) |
(423,000) |
(1,711,000) |
(843,000) |
| Assets, Realized Gain/(Loss) |
111,000 |
0 |
111,000 |
97,000 |
| Assets, Change in Net Unrealized Gain/(Loss) |
(314,000) |
(2,169,000) |
(679,000) |
(2,320,000) |
| Assets, Purchases |
1,057,000 |
2,826,000 |
1,929,000 |
9,682,000 |
| Assets, Sales |
(1,160,000) |
0 |
(1,160,000) |
(1,155,000) |
| Assets, Transfers In and/or Out of Level 3 |
0 |
0 |
0 |
0 |
| Assets, Ending Balance |
3,827,000 |
5,461,000 |
3,827,000 |
5,461,000 |
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Private Label Residential Mortgage-Backed Securities [Member] | Investments [Member]
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|
|
|
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| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
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|
|
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| Assets, Beginning Balance |
385,059,000 |
357,894,000 |
417,533,000 |
338,839,000 |
| Assets, Accreted Discounts/Amortized Premiums |
6,182,000 |
4,389,000 |
15,471,000 |
11,710,000 |
| Assets, Realized Gain/(Loss) |
5,440,000 |
3,107,000 |
12,489,000 |
17,664,000 |
| Assets, Change in Net Unrealized Gain/(Loss) |
24,013,000 |
(12,994,000) |
49,149,000 |
(35,632,000) |
| Assets, Purchases |
92,412,000 |
106,262,000 |
251,030,000 |
292,521,000 |
| Assets, Sales |
(55,181,000) |
(62,394,000) |
(287,747,000) |
(228,838,000) |
| Assets, Transfers In and/or Out of Level 3 |
0 |
0 |
0 |
0 |
| Assets, Ending Balance |
457,925,000 |
396,264,000 |
457,925,000 |
396,264,000 |
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Private Label Commercial Mortgage-Backed Securities [Member] | Investments [Member]
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|
|
|
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| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
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|
|
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| Assets, Beginning Balance |
28,405,000 |
10,942,000 |
16,093,000 |
1,850,000 |
| Assets, Accreted Discounts/Amortized Premiums |
271,000 |
147,000 |
527,000 |
378,000 |
| Assets, Realized Gain/(Loss) |
2,905,000 |
(38,000) |
3,213,000 |
859,000 |
| Assets, Change in Net Unrealized Gain/(Loss) |
(293,000) |
(1,707,000) |
990,000 |
(3,185,000) |
| Assets, Purchases |
57,195,000 |
6,918,000 |
79,911,000 |
23,669,000 |
| Assets, Sales |
(39,287,000) |
(1,383,000) |
(51,538,000) |
(8,692,000) |
| Assets, Transfers In and/or Out of Level 3 |
0 |
0 |
0 |
0 |
| Assets, Ending Balance |
49,196,000 |
14,879,000 |
49,196,000 |
14,879,000 |
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Commercial Mortgage Loans [Member] | Investments [Member]
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| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |
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|
|
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| Assets, Beginning Balance |
4,650,000 |
4,650,000 |
4,400,000 |
0 |
| Assets, Accreted Discounts/Amortized Premiums |
21,000 |
31,000 |
71,000 |
92,000 |
| Assets, Realized Gain/(Loss) |
0 |
0 |
0 |
0 |
| Assets, Change in Net Unrealized Gain/(Loss) |
(21,000) |
(306,000) |
179,000 |
(392,000) |
| Assets, Purchases |
0 |
0 |
0 |
4,675,000 |
| Assets, Sales |
0 |
0 |
0 |
0 |
| Assets, Transfers In and/or Out of Level 3 |
0 |
0 |
0 |
0 |
| Assets, Ending Balance |
$ 4,650,000 |
$ 4,375,000 |
$ 4,650,000 |
$ 4,375,000 |