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Segment Information - Schedule of fiduciary investment income by business segment (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Fiduciary investment income | $ 5 | $ 6 | $ 5 | $ 5 | $ 7 | $ 7 | $ 6 | $ 6 | $ 21 | $ 26 | $ 28
HR Solutions [Member] |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Fiduciary investment income |  |  |  |  |  |  |  |  | 0 | 0 | 0
Risk Solutions [Member] |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Fiduciary investment income |  |  |  |  |  |  |  |  | $ 21 | $ 26 | $ 28

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- Definition Income earned on the interest-bearing assets used as temporary investments of premiums collected from insured's but not yet remitted to insurance companies. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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