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Reinsurance (List of Direct, Assumed, and Ceded Reinsurance Amounts) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Premiums written: |  |  |  |
Direct | $ 753,363 | $ 706,408 | $ 1,467,597 | $ 1,390,228
Assumed | 6,536 | 6,488 | 12,807 | 12,179
Ceded | (104,651) | (99,082) | (200,596) | (189,889)
Net | 655,248 | 613,814 | 1,279,808 | 1,212,518
Premiums earned: |  |  |  |
Direct | 696,723 | 654,588 | 1,380,456 | 1,301,316
Assumed | 6,612 | 6,063 | 12,736 | 11,842
Ceded | (98,499) | (92,621) | (196,528) | (184,274)
Net | 604,836 | 568,030 | 1,196,664 | 1,128,884
Loss and loss expenses incurred: |  |  |  |
Direct | 391,014 | 389,550 | 811,930 | 731,672
Assumed | 2,364 | 7,766 | 10,368 | 12,203
Ceded | (27,050) | (55,757) | (71,029) | (84,844)
Net | 366,328 | 341,559 | 751,269 | 659,031
National Flood Insurance Program [Member] |  |  |  |
Premiums written: |  |  |  |
Ceded | (66,341) | (63,808) | (123,010) | (120,142)
Premiums earned: |  |  |  |
Ceded | (60,143) | (57,655) | (119,134) | (114,932)
Loss and loss expenses incurred: |  |  |  |
Ceded | $ (10,261) | $ (15,140) | $ (25,980) | $ (21,681)

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