Actuarial Assumptions used to Compute Net Periodic Pension Cost (Details) - UNITED KINGDOM	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted-average discount rate	3.80%	3.50%	4.60%
Weighted-average long-term rate of return on plan assets	5.30%	5.60%	5.90%