Summary of Fair Value of Plan Assets by Asset Category (Parenthetical) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Cash
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, target plan asset allocations	13.00%
UNITED KINGDOM | Bonds | Balanced Fund
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, target plan asset allocations	24.00%	32.00%
UNITED KINGDOM | Bonds | Growth Funds
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, target plan asset allocations	12.00%	8.00%
UNITED KINGDOM | Equity Securities | Balanced Fund
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, target plan asset allocations	52.00%	54.00%
UNITED KINGDOM | Equity Securities | Growth Funds
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, target plan asset allocations	67.00%	67.00%
UNITED KINGDOM | Other Asset | Balanced Fund
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, target plan asset allocations	9.00%	5.00%
UNITED KINGDOM | Other Asset | Growth Funds
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, target plan asset allocations	9.00%	15.00%
UNITED KINGDOM | Cash | Balanced Fund
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, target plan asset allocations	15.00%	9.00%
UNITED KINGDOM | Cash | Growth Funds
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, target plan asset allocations	12.00%	10.00%