v2.4.0.6
Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Level 3 Inputs) (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Balance at beginning of the period $ 494,520 $ 472,021 $ 452,813 $ 400,386
Total unrealized gains (losses)        
Included in net investment income (13,076) 5,573 16,108 29,371
Included in other income (loss) (15,576) 91 2,987 41,599
Total realized gains        
Included in net investment income 0 0 0 0
Included in other income (loss) 22,076 3,307 (33,232) 12,822
Total foreign exchange losses (1,023) 462 (670) 1,780
Purchases 46,834 20,203 68,804 39,299
Sales (91,655) (6,864) (105,086) (11,024)
Settlements 10,365 (19,414) 50,741 (38,854)
Net transfers into Level 3 0 0 0 0
Balance at end of the period 452,465 475,379 452,465 475,379
Change in unrealized gains (losses) for the period included in earnings for assets held at the end of the period included in net investment income (13,076) 5,573 16,108 29,371
Change in unrealized gains (losses) for the period included in earnings for assets held at the end of the period included in other income (loss) 8,019 4,195 9,678 48,598
Fixed maturity investments [Member]
        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Balance at beginning of the period 27,838 21,826 27,761 21,785
Total unrealized gains (losses)        
Included in net investment income (63) (562) 14 (521)
Included in other income (loss) 0 0 0 0
Total realized gains        
Included in net investment income 0 0 0 0
Included in other income (loss) 0 0 0 0
Total foreign exchange losses 0 0 0 0
Purchases 0 0 0 0
Sales 0 0 0 0
Settlements 0 0 0 0
Net transfers into Level 3 0 0 0 0
Balance at end of the period 27,775 21,264 27,775 21,264
Change in unrealized gains (losses) for the period included in earnings for assets held at the end of the period included in net investment income (63) (562) 14 (521)
Change in unrealized gains (losses) for the period included in earnings for assets held at the end of the period included in other income (loss) 0 0 0 0
Other Investments [Member]
        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Balance at beginning of the period 418,537 381,815 396,526 362,102
Total unrealized gains (losses)        
Included in net investment income (13,013) 6,135 16,094 29,892
Included in other income (loss) 0 0 0 0
Total realized gains        
Included in net investment income 0 0 0 0
Included in other income (loss) 0 0 0 0
Total foreign exchange losses (1,394) 553 (664) 1,922
Purchases 5,956 11,219 18,645 28,684
Sales 0 0 0 0
Settlements (19,581) (18,599) (40,096) (41,477)
Net transfers into Level 3 0 0 0 0
Balance at end of the period 390,505 381,123 390,505 381,123
Change in unrealized gains (losses) for the period included in earnings for assets held at the end of the period included in net investment income (13,013) 6,135 16,094 29,892
Change in unrealized gains (losses) for the period included in earnings for assets held at the end of the period included in other income (loss) 0 0 0 0
Other Assets and (Liabilities) [Member]
        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Balance at beginning of the period 48,145 68,380 28,526 16,499
Total unrealized gains (losses)        
Included in net investment income 0 0 0 0
Included in other income (loss) (15,576) 91 2,987 41,599
Total realized gains        
Included in net investment income 0 0 0 0
Included in other income (loss) 22,076 3,307 (33,232) 12,822
Total foreign exchange losses 371 (91) (6) (142)
Purchases 40,878 8,984 50,159 10,615
Sales (91,655) (6,864) (105,086) (11,024)
Settlements 29,946 (815) 90,837 2,623
Net transfers into Level 3 0 0 0 0
Balance at end of the period 34,185 72,992 34,185 72,992
Change in unrealized gains (losses) for the period included in earnings for assets held at the end of the period included in net investment income 0 0 0 0
Change in unrealized gains (losses) for the period included in earnings for assets held at the end of the period included in other income (loss) $ 8,019 $ 4,195 $ 9,678 $ 48,598