| FINANCIAL INSTRUMENTS MEASURED AT FAIR VALUE ON A RECURRING BASIS [Table Text Block] |
| | | | | | | | | | | | | | | | | | | | | Quoted Prices in Active Markets for Identical Assets (Level 1) | | Significant Other Observable Inputs (Level 2) | | Significant Unobservable Inputs (Level 3) | | Total Fair Value | | | | | | | | | | | | | At December 31, 2013 | | | | | | | | | | Assets | | | | | | | | | | Fixed maturities | | | | | | | | | | U.S. government and agency | $ | 1,119,632 |
| | $ | 269,066 |
| | $ | — |
| | $ | 1,388,698 |
| | | Non-U.S. government | — |
| | 1,176,382 |
| | — |
| | 1,176,382 |
| | | Corporate debt | — |
| | 3,608,238 |
| | — |
| | 3,608,238 |
| | | Agency RMBS | — |
| | 2,448,827 |
| | — |
| | 2,448,827 |
| | | CMBS | — |
| | 793,396 |
| | 4,018 |
| | 797,414 |
| | | Non-Agency RMBS | — |
| | 67,567 |
| | — |
| | 67,567 |
| | | ABS | — |
| | 922,652 |
| | 30,799 |
| | 953,451 |
| | | Municipals | — |
| | 1,545,750 |
| | — |
| | 1,545,750 |
| | | | 1,119,632 |
| | 10,831,878 |
| | 34,817 |
| | 11,986,327 |
| | | Equity securities | | | | | | | | | | Common stocks | 438,318 |
| | — |
| | — |
| | 438,318 |
| | | Exchange-traded funds | 138,847 |
| | — |
| | — |
| | 138,847 |
| | | Non-U.S. bond mutual funds | — |
| | 124,822 |
| | — |
| | 124,822 |
| | | | 577,165 |
| | 124,822 |
| | — |
| | 701,987 |
| | | Other investments | | | | | | | | | | Hedge funds | — |
| | 488,755 |
| | 461,055 |
| | 949,810 |
| | | Direct lending funds | — |
| | — |
| | 22,134 |
| | 22,134 |
| | | CLO-Equities | — |
| | — |
| | 73,866 |
| | 73,866 |
| | | | — |
| | 488,755 |
| | 557,055 |
| | 1,045,810 |
| | | Short-term investments | — |
| | 46,212 |
| | — |
| | 46,212 |
| | | Derivative instruments (see Note 7) | — |
| | 6,824 |
| | 984 |
| | 7,808 |
| | | Total Assets | $ | 1,696,797 |
| | $ | 11,498,491 |
| | $ | 592,856 |
| | $ | 13,788,144 |
| | | Liabilities | | | | | | | | | | Derivative instruments (see Note 7) | $ | — |
| | $ | 1,152 |
| | $ | 815 |
| | $ | 1,967 |
| | | Cash settled awards (see Note 16) | — |
| | 8,693 |
| | — |
| | 8,693 |
| | | Total Liabilities | $ | — |
| | $ | 9,845 |
| | $ | 815 |
| | $ | 10,660 |
| | | | | | | | | | | | | At December 31, 2012 | | | | | | | | | | Assets | | | | | | | | | | Fixed maturities | | | | | | | | | | U.S. government and agency | $ | 1,094,220 |
| | $ | 328,665 |
| | $ | — |
| | $ | 1,422,885 |
| | | Non-U.S. government | — |
| | 1,104,576 |
| | — |
| | 1,104,576 |
| | | Corporate debt | — |
| | 3,874,832 |
| | 1,550 |
| | 3,876,382 |
| | | Agency RMBS | — |
| | 2,659,908 |
| | — |
| | 2,659,908 |
| | | CMBS | — |
| | 835,788 |
| | 4,296 |
| | 840,084 |
| | | Non-Agency RMBS | — |
| | 94,089 |
| | 1,110 |
| | 95,199 |
| | | ABS | — |
| | 579,231 |
| | 63,975 |
| | 643,206 |
| | | Municipals | — |
| | 1,285,809 |
| | — |
| | 1,285,809 |
| | | | 1,094,220 |
| | 10,762,898 |
| | 70,931 |
| | 11,928,049 |
| | | Equity securities | | | | | | | | | | Common stocks | 443,398 |
| | — |
| | — |
| | 443,398 |
| | | Exchange-traded funds | 119,161 |
| | — |
| | — |
| | 119,161 |
| | | Non-U.S. bond mutual funds | — |
| | 103,989 |
| | — |
| | 103,989 |
| | | | 562,559 |
| | 103,989 |
| | — |
| | 666,548 |
| | | Other investments | | | | | | | | | | Hedge funds | — |
| | 421,006 |
| | 359,996 |
| | 781,002 |
| | | Direct lending funds | — |
| | — |
| | — |
| | — |
| | | CLO-Equities | — |
| | — |
| | 62,435 |
| | 62,435 |
| | | | — |
| | 421,006 |
| | 422,431 |
| | 843,437 |
| | | Short-term investments | — |
| | 108,860 |
| | — |
| | 108,860 |
| | | Derivative instruments (see Note 7) | — |
| | 5,838 |
| | — |
| | 5,838 |
| | | Total Assets | $ | 1,656,779 |
| | $ | 11,402,591 |
| | $ | 493,362 |
| | $ | 13,552,732 |
| | | Liabilities | | | | | | | | | | Derivative instruments (see Note 7) | $ | — |
| | $ | 3,737 |
| | $ | — |
| | $ | 3,737 |
| | | Cash settled awards (see Note 16) | — |
| | — |
| | — |
| | — |
| | | Total Liabilities | $ | — |
| | $ | 3,737 |
| | $ | — |
| | $ | 3,737 |
| | | | | | | | | | | |
|
| CHANGES IN LEVEL 3 FINANCIAL INSTRUMENTS MEASURED AT FAIR VALUE ON A RECURRING BASIS [Table Text Block] |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Opening Balance | | Transfers into Level 3 | | Transfers out of Level 3 | | Included in earnings (1) | | Included in OCI (2) | | Purchases | | Sales | | Settlements/ Distributions | | Closing Balance | | Change in unrealized investment gain/loss (3) | | | | | | | | | | | | | | | | | | | | | | | | | Year ended December 31, 2013 | | | | | | | | | | | | | | | | | | | Fixed maturities | | | | | | | | | | | | | | | | | | | | | | Corporate debt | $ | 1,550 |
| | $ | — |
| | $ | — |
| | $ | 1,550 |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | (3,100 | ) | | $ | — |
| | $ | — |
| | | Non-Agency RMBS | 1,110 |
| | — |
| | (1,222 | ) | | — |
| | 135 |
| | — |
| | — |
| | (23 | ) | | — |
| | — |
| | | CMBS | 4,296 |
| | — |
| | — |
| | — |
| | (278 | ) | | — |
| | — |
| | — |
| | 4,018 |
| | — |
| | | ABS | 63,975 |
| | — |
| | — |
| | (111 | ) | | 1,794 |
| | — |
| | — |
| | (34,859 | ) | | 30,799 |
| | — |
| | | | 70,931 |
| | — |
| | (1,222 | ) | | 1,439 |
| | 1,651 |
| | — |
| | — |
| | (37,982 | ) | | 34,817 |
| | — |
| | | Other investments | | | | | | | | | | | | | | | | | | | | | Hedge funds | 359,996 |
| | — |
| | — |
| | 58,293 |
| | — |
| | 86,138 |
| | — |
| | (43,372 | ) | | 461,055 |
| | 58,293 |
| | | Direct lending funds | — |
| | — |
| | — |
| | (125 | ) | | — |
| | 22,317 |
| | — |
| | (58 | ) | | 22,134 |
| | (125 | ) | | | CLO-Equities | 62,435 |
| | — |
| | — |
| | 27,898 |
| | — |
| | 34,016 |
| | — |
| | (50,483 | ) | | 73,866 |
| | 27,898 |
| | | | 422,431 |
| | — |
| | — |
| | 86,066 |
| | — |
| | 142,471 |
| | — |
| | (93,913 | ) | | 557,055 |
| | 86,066 |
| | | Other assets | | | | | | | | | | | | | | | | | | | | | Derivative instruments | — |
| | — |
| | — |
| | 2,084 |
| | — |
| | (1,100 | ) | | — |
| | — |
| | 984 |
| | 2,084 |
| | | | — |
| | — |
| | — |
| | 2,084 |
| | — |
| | (1,100 | ) | | — |
| | — |
| | 984 |
| | 2,084 |
| | | Total assets | $ | 493,362 |
| | $ | — |
| | $ | (1,222 | ) | | $ | 89,589 |
| | $ | 1,651 |
| | $ | 141,371 |
| | $ | — |
| | $ | (131,895 | ) | | $ | 592,856 |
| | $ | 88,150 |
| | | | | | | | | | | | | | | | | | | | | | |
| | | Other liabilities | | | | | | | | | | | | | | | | | | | | | Derivative instruments | — |
| | — |
| | — |
| | 98 |
| | — |
| | 717 |
| | — |
| | — |
| | 815 |
| | 98 |
| | | Total liabilities | $ | — |
| | $ | — |
| | $ | — |
| | $ | 98 |
| | $ | — |
| | $ | 717 |
| | $ | — |
| | $ | — |
| | $ | 815 |
| | $ | 98 |
| | | | | | | | | | | | | | | | | | | | | | | | | Year ended December 31, 2012 | | | | | | | | | | | | | | | | | | | Fixed maturities | | | | | | | | | | | | | | | | | | | | | | Corporate debt | $ | 1,550 |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | 1,550 |
| | $ | — |
| | | Non-Agency RMBS | — |
| | 1,110 |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | 1,110 |
| | — |
| | | CMBS | — |
| | 4,296 |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | 4,296 |
| | — |
| | | ABS | 49,328 |
| | 10,539 |
| | — |
| | — |
| | 5,112 |
| | — |
| | — |
| | (1,004 | ) | | 63,975 |
| | — |
| | | | 50,878 |
| | 15,945 |
| | — |
| | — |
| | 5,112 |
| | — |
| | — |
| | (1,004 | ) | | 70,931 |
| | — |
| | | Other investments | | | | | | | | | | | | | | | | | | | | | Hedge funds | 346,244 |
| | — |
| | (9,435 | ) | | 33,301 |
| | — |
| | — |
| | (2,835 | ) | | (7,279 | ) | | 359,996 |
| | 33,301 |
| | | Direct lending funds | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | | CLO-Equities | 66,560 |
| | — |
| | — |
| | 31,108 |
| | — |
| | — |
| | — |
| | (35,233 | ) | | 62,435 |
| | 31,108 |
| | | | 412,804 |
| | — |
| | (9,435 | ) | | 64,409 |
| | — |
| | — |
| | (2,835 | ) | | (42,512 | ) | | 422,431 |
| | 64,409 |
| | | Other assets | | | | | | | | | | | | | | | | | | | | | Derivative instruments | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | | | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | | Total assets | $ | 463,682 |
| | $ | 15,945 |
| | $ | (9,435 | ) | | $ | 64,409 |
| | $ | 5,112 |
| | $ | — |
| | $ | (2,835 | ) | | $ | (43,516 | ) | | $ | 493,362 |
| | $ | 64,409 |
| | | | | | | | | | | | | | | | | | | | | | | | | Other liabilities | | | | | | | | | | | | | | | | | | | | | Derivative instruments | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | | Total liabilities | $ | — |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | — |
| | | | | | | | | | | | | | | | | | | | | | | |
| | (1) | Gains and losses included in earnings on fixed maturities are included in net realized investment gains (losses). Gains and (losses) included in earnings on other investments are included in net investment income. Gains (losses) on weather derivatives included in earnings are included in other insurance-related income. |
| | (2) | Gains and losses included in other comprehensive income (“OCI”) on fixed maturities are included in unrealized gains (losses) arising during the period. |
| | (3) | Change in unrealized investment gain/(loss) relating to assets held at the reporting date. |
|