Provision for post-employment benefits - Movement in Pension Plan Liabilities (Detail) - GBP (£) £ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of net defined benefit (liability) asset
Plan liabilities at beginning of year	£ 206.3	£ 276.5
Plan liabilities at end of year	184.3	206.3	£ 276.5
Retirement benefit obligation [member]
Disclosure of net defined benefit (liability) asset
Plan liabilities at beginning of year	1,135.4	1,209.8	1,039.9
Service cost	15.5	13.0	22.4
Interest cost	30.7	32.9	37.2
Effect of changes in demographic assumptions	(3.8)	(12.7)	(6.7)
Effect of changes in financial assumptions	(45.2)	17.0	92.6
Effect of experience adjustments	(3.8)	(7.9)	(1.0)
Benefits paid	(75.6)	(79.7)	(92.4)
Loss/(gain) due to exchange rate movements	30.0	(36.4)	124.2
Settlement payments	(70.4)	(1.2)	(4.8)
Other	11.2	0.6	(1.6)
Plan liabilities at end of year	£ 1,024.0	£ 1,135.4	£ 1,209.8

The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in demographic assumptions that result in remeasurements of the net defined benefit liability (asset). Demographic assumptions deal with matters such as: (a) mortality; (b) rates of employee turnover, disability and early retirement; (c) the proportion of plan members with dependants who will be eligible for benefits; (d) the proportion of plan members who will select each form of payment option available under the plan terms; and (e) claim rates under medical plans. [Refer: Net defined benefit liability (asset)]

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- Definition

The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in financial assumptions that result in remeasurements of the net defined benefit liability (asset). Financial assumptions deal with items such as: (a) the discount rate; (b) benefit levels, excluding any cost of the benefits to be met by employees, and future salary; (c) in the case of medical benefits, future medical costs, including claim handling costs (ie the costs that will be incurred in processing and resolving claims, including legal and adjuster's fees); and (d) taxes payable by the plan on contributions relating to service before the reporting date or on benefits resulting from that service. [Refer: Net defined benefit liability (asset)]

+ References

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- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from employee service in the current period. [Refer: Net defined benefit liability (asset)]

+ References

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Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

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The increase (decrease) in the net defined benefit liability (asset) resulting from changes in foreign exchange rates. [Refer: Net defined benefit liability (asset)]

+ References

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The increase (decrease) in the net defined benefit liability (asset) resulting from changes that the entity does not separately disclose in the same statement or note. [Refer: Net defined benefit liability (asset)]

+ References

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- Definition

The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling. [Refer: Defined benefit plans [member]]

+ References

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The decrease (increase) in the net defined benefit liability (asset) resulting from payments from the plan. [Refer: Net defined benefit liability (asset)]

+ References

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The decrease (increase) in the net defined benefit liability (asset) resulting from payments from the plan in respect of settlements. [Refer: Gains (losses) arising from settlements, net defined benefit liability (asset); Net defined benefit liability (asset); Defined benefit plans [member]]

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- Definition

Experience gain/(loss) arising on the plan liabilities.

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Interest cost on plan liabilities

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