Pension Arrangements (Components Of U.K. Pension Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 336,189	$ 297,854	$ 298,319
Growth assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	227,140	200,787
Total debt securities, % of total	67.60%	67.40%
Debt securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	104,361	93,182
Total debt securities, % of total	31.00%	31.30%
Debt securities | Government [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	22,702	25,115
Total debt securities, % of total	6.80%	8.40%
Debt securities | Corporate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	28,267	20,581
Total debt securities, % of total	8.40%	6.90%
Debt securities | Index-Linked [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	53,392	47,486
Total debt securities, % of total	15.90%	15.90%
Real estate mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	2,479	2,325
Total debt securities, % of total	0.70%	0.80%
Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 2,209	$ 1,560
Total debt securities, % of total	0.70%	0.50%