Pension Arrangements (Components Of U.K. Pension Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 410,928	$ 397,469	$ 336,189
Growth assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	247,393	280,019
Total debt securities, % of total	60.20%	70.50%
Debt securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	158,436	113,393
Total debt securities, % of total	38.60%	28.50%
Debt securities | Corporate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	37,929	30,774
Total debt securities, % of total	9.20%	7.70%
Debt securities | Index-Linked [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	120,507	82,619
Total debt securities, % of total	29.30%	20.80%
Real estate mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	2,976	2,746
Total debt securities, % of total	0.70%	0.70%
Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 2,123	$ 1,311
Total debt securities, % of total	0.50%	0.30%