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v3.7.0.1

Investments (Details) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2017 USD ($) security | Mar. 31, 2016 USD ($) | Dec. 31, 2016 USD ($) security
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | $ 4,662,620,000 |  | $ 4,724,355,000
Gross Unrealized Gains | 35,434,000 |  | 28,628,000
Gross Unrealized Losses | (48,773,000) |  | (60,633,000)
Fair Value | 4,649,281,000 |  | 4,692,350,000
Other-than-temporary impairments | $ 0 |  | 0
Federal Home Loan Bank advances, collateral, value of principal, percent (as a percent) | 102.00% |  |
FHLB advance collateral | $ 165,000,000 |  |
Gross accumulated unrealized gain (losses) on available-for-sale securities | $ (48,800,000) |  | $ (60,600,000)
Number of securities in unrealized loss position (in securities) | security | 495 |  | 607
Net impairment losses recognized in earnings | $ 0 | $ 0 |
Total debt securities |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 4,655,457,000 |  | $ 4,717,211,000
Gross Unrealized Gains | 35,414,000 |  | 28,620,000
Gross Unrealized Losses | (48,752,000) |  | (60,609,000)
Fair Value | 4,642,119,000 |  | 4,685,222,000
U.S. Treasury securities and obligations of U.S. government corporations and agencies |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 61,035,000 |  | 73,847,000
Gross Unrealized Gains | 387,000 |  | 407,000
Gross Unrealized Losses | (604,000) |  | (724,000)
Fair Value | 60,818,000 |  | 73,530,000
Obligations of U.S. states and political subdivisions |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 2,161,765,000 |  | 2,147,458,000
Gross Unrealized Gains | 25,893,000 |  | 20,983,000
Gross Unrealized Losses | (19,208,000) |  | (25,425,000)
Fair Value | 2,168,450,000 |  | 2,143,016,000
Corporate debt securities |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 1,753,470,000 |  | 1,756,461,000
Gross Unrealized Gains | 7,594,000 |  | 6,059,000
Gross Unrealized Losses | (13,724,000) |  | (18,610,000)
Fair Value | 1,747,340,000 |  | 1,743,910,000
ABS |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 37,107,000 |  | 59,519,000
Gross Unrealized Gains | 29,000 |  | 74,000
Gross Unrealized Losses | (19,000) |  | (28,000)
Fair Value | 37,117,000 |  | 59,565,000
RMBS |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 220,739,000 |  | 231,733,000
Gross Unrealized Gains | 93,000 |  | 102,000
Gross Unrealized Losses | (7,923,000) |  | (7,626,000)
Fair Value | 212,909,000 |  | 224,209,000
CMBS |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 300,185,000 |  | 327,042,000
Gross Unrealized Gains | 1,038,000 |  | 769,000
Gross Unrealized Losses | (7,106,000) |  | (7,994,000)
Fair Value | 294,117,000 |  | 319,817,000
CLOs |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 121,156,000 |  | 121,151,000
Gross Unrealized Gains | 380,000 |  | 226,000
Gross Unrealized Losses | (168,000) |  | (202,000)
Fair Value | 121,368,000 |  | 121,175,000
Equity securities |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 7,163,000 |  | 7,144,000
Gross Unrealized Gains | 20,000 |  | 8,000
Gross Unrealized Losses | (21,000) |  | (24,000)
Fair Value | $ 7,162,000 |  | $ 7,128,000

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