v3.3.1.900

Fair Value Measurements - Fair Value Hierarchy (Details)	Dec. 31, 2015 USD ($) security	Dec. 31, 2014 USD ($) security
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, number of securities | security	2	1
Other investments	$ 11,812,000	$ 12,571,000
Investments in limited partnerships
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	$ 5,907,000	5,581,000
Other investments, percent of assets	0.10%
Significant Other Observable Inputs (Level 2) | Available-for-sale fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets valued using market approach, amount	$ 4,943,000	5,016,000
Fair Value, Measurements, Recurring | Total Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, fair value	11,812,000	12,571,000
Total assets fair value	$ 3,519,900,000	$ 3,469,475,000
Percentage of total assets	61.60%	67.20%
Fair Value, Measurements, Recurring | Total Fair Value | Available-for-sale fixed maturities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets valued by third party, percentage	99.90%	99.90%
Assets valued using market approach, percentage (in securities)	0.10%	0.10%
Fair Value, Measurements, Recurring | Total Fair Value | U.S. treasury bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	$ 6,010,000	$ 9,360,000
Fair Value, Measurements, Recurring | Total Fair Value | U.S. agency bonds – mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	1,476,991,000	1,322,443,000
Fair Value, Measurements, Recurring | Total Fair Value | U.S. agency bonds – other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	24,311,000	7,988,000
Fair Value, Measurements, Recurring | Total Fair Value | Non-U.S. government and supranational bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	30,544,000	51,643,000
Fair Value, Measurements, Recurring | Total Fair Value | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	165,804,000	54,780,000
Fair Value, Measurements, Recurring | Total Fair Value | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	1,739,668,000	1,895,379,000
Fair Value, Measurements, Recurring | Total Fair Value | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	64,760,000	65,819,000
Fair Value, Measurements, Recurring | Total Fair Value | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value		49,492,000
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, fair value	4,905,000	5,990,000
Total assets fair value	$ 10,915,000	$ 15,350,000
Percentage of total assets	0.20%	0.30%
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. treasury bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	$ 6,010,000	$ 9,360,000
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. agency bonds – mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. agency bonds – other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Non-U.S. government and supranational bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value		0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, fair value	0	0
Total assets fair value	$ 3,502,078,000	$ 3,447,544,000
Percentage of total assets	61.30%	66.80%
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. treasury bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	$ 0	$ 0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. agency bonds – mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	1,476,991,000	1,322,443,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. agency bonds – other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	24,311,000	7,988,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Non-U.S. government and supranational bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	30,544,000	51,643,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	165,804,000	54,780,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	1,739,668,000	1,895,379,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	64,760,000	65,819,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value		49,492,000
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, fair value	6,907,000	6,581,000
Total assets fair value	$ 6,907,000	$ 6,581,000
Percentage of total assets	0.10%	0.10%
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. treasury bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	$ 0	$ 0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. agency bonds – mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. agency bonds – other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Non-U.S. government and supranational bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS fixed maturities, fair value		$ 0
Preferred stock | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	$ 1,000,000

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Other investments not otherwise specified in the taxonomy.

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