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Acquisitions (Details Textual) (USD $) In Millions, unless otherwise specified | 3 Months Ended |  | 0 Months Ended |  | 0 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | ---
Mar. 31, 2014 | Mar. 31, 2013 | Dec. 31, 2013 | Mar. 27, 2014 Selective Insurance Company of America Self-Insured Pooled Group [Member] | Apr. 01, 2014 Summit Holdings Southeast, Inc [Member] | Apr. 01, 2014 Subsequent Event [Member] Summit Holdings Southeast, Inc [Member] | Dec. 31, 2013 Minimum [Member] Summit Holdings Southeast, Inc [Member]
Business Acquisition [Line Items] |  |  |  |  |  |  |
Payments to acquire business | $ 8 | $ 0 |  | $ 8 |  | $ 260 |
In-force gross written premiums of acquired book of business |  |  |  | 38 |  |  |
Capital contributions in acquired business |  |  |  |  |  | 140 |
Total capital investment in acquired business |  |  |  |  |  | 400 |
Total assets of acquired business | 42,770 |  | 42,087 |  | 1,500 |  |
Net written premiums of acquired business |  |  |  |  |  |  | $ 500

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