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Reinsurance (List of Direct, Assumed, and Ceded Reinsurance Amounts) (Details) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2016 | Mar. 31, 2015
Premiums written: |  |
Direct | $ 646,278 | $ 598,783
Assumed | 6,320 | 6,081
Ceded premiums written | (87,239) | (86,776)
Net | 565,359 | 518,088
Premiums earned: |  |
Direct | 606,661 | 562,042
Assumed | 6,270 | 5,908
Ceded premiums earned | (90,473) | (91,827)
Net | 522,458 | 476,123
Loss and loss expense incurred: |  |
Direct | 361,639 | 312,246
Assumed | 6,355 | 4,662
Ceded loss and loss expense incurred | (70,850) | (31,909)
Net | 297,144 | 284,999
National Flood Insurance Program [Member] |  |
Premiums written: |  |
Ceded premiums written | (53,248) | (53,842)
Premiums earned: |  |
Ceded premiums earned | (56,814) | (58,998)
Loss and loss expense incurred: |  |
Ceded loss and loss expense incurred | $ (40,718) | $ (6,249)

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