Pension Arrangements (Components Of Net Pension Benefits Related To U.K. Pension Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Service cost	$ 3,662	$ 4,087	$ 3,852
Interest cost	13,143	13,660	13,887
Expected return on plan assets	(19,609)	(23,255)	(21,450)
Amortization of prior service cost	0	0	11
Net pension benefit	$ (2,804)	$ (5,508)	$ (3,700)