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Fair Value Measurements - Fair Value Hierarchy (Details) (USD $)
In Thousands, unless otherwise specified |
0 Months Ended | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Mar. 31, 2014
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Dec. 31, 2013
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Mar. 31, 2014
Investments in limited partnerships [Member]
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Dec. 31, 2013
Investments in limited partnerships [Member]
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Mar. 31, 2014
Other [Member]
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Dec. 31, 2013
Other [Member]
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Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
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Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
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Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
U.S. treasury bonds [Member]
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Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
U.S. treasury bonds [Member]
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Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
U.S. agency bonds – mortgage-backed [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
U.S. agency bonds – mortgage-backed [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
U.S. agency bonds – other [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
U.S. agency bonds – other [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Non-U.S. government bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Non-U.S. government bonds [Member]
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Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Other mortgage-backed securities [Member]
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Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Other mortgage-backed securities [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Corporate bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Corporate bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Municipal bonds – auction rate [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Municipal bonds – other [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Municipal bonds – other [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
U.S. treasury bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
U.S. treasury bonds [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
U.S. agency bonds – mortgage-backed [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
U.S. agency bonds – mortgage-backed [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
U.S. agency bonds – other [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
U.S. agency bonds – other [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
Non-U.S. government bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
Non-U.S. government bonds [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
Other mortgage-backed securities [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
Other mortgage-backed securities [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
Corporate bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
Corporate bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
Municipal bonds – auction rate [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
Municipal bonds – other [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
Municipal bonds – other [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
U.S. treasury bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
U.S. treasury bonds [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
U.S. agency bonds – mortgage-backed [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
U.S. agency bonds – mortgage-backed [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
U.S. agency bonds – other [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
U.S. agency bonds – other [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
Non-U.S. government bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
Non-U.S. government bonds [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
Other mortgage-backed securities [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
Other mortgage-backed securities [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
Corporate bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
Corporate bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
Municipal bonds – auction rate [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
Municipal bonds – other [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
Municipal bonds – other [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
Fixed Maturities [Member]
securities
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
Fixed Maturities [Member]
securities
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
U.S. treasury bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
U.S. treasury bonds [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
U.S. agency bonds – mortgage-backed [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
U.S. agency bonds – mortgage-backed [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
U.S. agency bonds – other [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
U.S. agency bonds – other [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
Non-U.S. government bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
Non-U.S. government bonds [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
Other mortgage-backed securities [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
Other mortgage-backed securities [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
Corporate bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
Corporate bonds [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
Municipal bonds – auction rate [Member]
|
Mar. 31, 2014
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
Municipal bonds – other [Member]
|
Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Total Fair Value [Member]
Municipal bonds – other [Member]
|
Jan. 15, 2014
Junior subordinated debt [Member]
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Extinguishment of debt, amount | $ 126,381 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Fixed maturities, fair value | 17,135 | 17,209 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1,235,470 | 1,262,655 | 8,196 | 8,108 | 73,965 | 73,212 | 44,368 | 33,444 | 1,725,768 | 1,606,700 | 99,170 | 63,917 | 61,569 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 17,135 | 17,209 | 1,235,470 | 1,262,655 | 8,196 | 8,108 | 73,965 | 73,212 | 44,368 | 33,444 | 1,725,768 | 1,606,700 | 99,170 | 63,917 | 61,569 | |||||||||||||||||
| Other investments, fair value | 0 | 0 | 0 | 0 | 5,773 | 5,092 | 5,773 | 5,092 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Total | 17,135 | 17,209 | 3,151,684 | 3,144,858 | 5,773 | 5,092 | 3,174,592 | 3,167,159 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Percentage of total assets | 0.40% | 0.40% | 64.70% | 66.70% | 0.10% | 0.10% | 65.20% | 67.20% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Assets, valued by third party, percentage | 99.90% | 95.30% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Assets, valued using market approach, percentage | 0.10% | 4.70% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Assets, valued using market approach, number | 2 | 5 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Assets, valued using market approach, amount | 3,411 | 150,298 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Other investments | $ 5,773 | $ 5,092 | $ 4,773 | $ 4,092 | $ 1,000 | $ 1,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Other investments, percent of assets | 0.20% | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||