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Commitments and Contingencies - Legal Narrative (Details) £ in Millions, SFr in Millions, NZD in Millions |  |  |  |  |  | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2016 USD ($) | Jun. 29, 2015 NZD | Jan. 26, 2015 USD ($) | Jan. 26, 2015 CHF (SFr) | Dec. 02, 2014 USD ($) | Dec. 02, 2014 CHF (SFr) | Jun. 01, 2007 USD ($) | Jun. 01, 2007 CHF (SFr) | Aug. 31, 2015 USD ($) | Jun. 30, 2015 GBP (£) | Mar. 31, 2015 USD ($) | May 31, 2010 USD ($) | Dec. 31, 2016 GBP (£) | Dec. 31, 2016 USD ($) | Dec. 20, 2016 GBP (£) | Apr. 30, 2014 GBP (£)
Potential Claim for Pension Advisory Services |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimate of possible loss | $ 55,000,000 |  |  |  |  |  |  |  |  |  |  |  |  | $ 55,000,000 |  | £ 45
Opry Mills Mall Limited Partnership |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Value of damages sought |  |  |  |  |  |  |  |  |  |  |  | $ 200,000,000 |  |  |  |
Amount of coverage for damages contended by the insurers |  |  |  |  |  |  |  |  |  |  |  | 50,000,000 |  |  |  |
Difference amount of damages sought by the client |  |  |  |  |  |  |  |  |  |  |  | $ 150,000,000 |  |  |  |
Opry Mills Mall Limited Partnership |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Damages awarded |  |  |  |  |  |  |  |  | $ 204,000,000 |  | $ 200,000,000 |  |  |  |  |
International Road Transport Union | Litigation Foreign Currency Denominated Award |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Value of damages sought |  |  |  |  |  |  |  | SFr 46.0 |  |  |  |  |  | 45,000,000 |  |
Damages awarded excluding interest and costs |  |  |  |  |  | SFr 16.8 |  |  |  |  |  |  |  | 16,000,000 |  |
Damages awarded |  |  |  |  |  | SFr 27.9 |  |  |  |  |  |  |  | 27,000,000 |  |
Litigation settlement |  |  | $ 14,000,000 | SFr 12.8 |  |  |  |  |  |  |  |  |  |  |  |
Settlement agreement terms maximum liability | 8,000,000 |  |  | SFr 8.7 |  |  |  |  |  |  |  |  |  |  |  |
International Road Transport Union | Litigation USD Denominated Award |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Value of damages sought |  |  |  |  |  |  | $ 3,000,000 |  |  |  |  |  |  |  |  |
Damages awarded excluding interest and costs |  |  |  |  | $ 3,000,000 |  |  |  |  |  |  |  |  |  |  |
Damages awarded |  |  |  |  | $ 5,000,000 |  |  |  |  |  |  |  |  |  |  |
Litigation settlement |  |  | 4,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement agreement terms maximum liability |  |  | $ 115,000 |  |  |  |  |  |  |  |  |  |  |  |  |
International Road Transport Union | Litigation Expenses and Interest |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Value of damages sought |  |  |  |  |  |  | $ 30,000,000 |  |  |  |  |  |  |  |  |
Trustees of Gleeds Pension Fund 2016 | Potential Claim for Pension Advisory Services |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimate of possible loss | 86,000,000 |  |  |  |  |  |  |  |  |  |  |  |  | 86,000,000 | £ 70 |
Philips |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Value of damages sought |  |  |  |  |  |  |  |  |  |  |  |  | £ 189 | 232,000,000 |  |
Philips 2015 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Value of damages sought |  |  |  |  |  |  |  |  |  | £ 290 |  |  |  | 356,000,000 |  |
Pending Litigation | Lyttleton Port Company Limited |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Value of damages sought |  | NZD 184 |  |  |  |  |  |  |  |  |  |  |  | 127,000,000 |  |
Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimate of possible loss | 0 |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |
Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimate of possible loss | $ 200,000,000 |  |  |  |  |  |  |  |  |  |  |  |  | $ 200,000,000 |  |

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