Pension Arrangements (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	$ 367,200,000	$ 344,000,000
Net unrecognized losses related to defined benefit pension plan (see Note 17)	(9,787,000)	(4,065,000)	(13,222,000)
Threshold For Recognizing net actuarial gains (losses)	10.00%
Expected Remaining Service Lives	11 years 8 months 12 days
Market value of plan assets changes period	5 years
Pre tax amount expected to be recognized in following year	4,000,000
Expected amount of net loss (gain) related to pension	3,200,000
Percentage of active employees in defined benefit plan	12.00%
Percentage Of Defined Benefit Plan Growth Assets	60.00%			60.00%
Target Investment Allocation Percentage in Debt Securities	40.00%			40.00%
Employer contributions	2,740,000	20,268,000
Expected contributions to U.K. pension plan	2,200,000
Retirement Savings Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued discretionary contribution	1,300,000	1,200,000	1,200,000
Accrued discretionary contribution, percentage	2.00%		3.00%
Pension (expense) benefit	2,400,000	2,300,000	2,000,000
Deferred Compensation Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued discretionary contribution	400,000	400,000	500,000
Accrued discretionary contribution, percentage	2.00%	2.00%	3.00%
DCP Liability	49,600,000	51,800,000
Gains (losses) in deemed participant investments	1,900,000	5,100,000	3,200,000
Net gains (losses) related to COLI and mutual fund investments	300,000	3,700,000	2,400,000
Pension (expense) benefit	900,000	900,000	1,000,000
U.K. Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension (expense) benefit	2,200,000	1,300,000	1,000,000
Accumulated Other Comprehensive Loss, net of taxes not yet recognized	$ (44,000,000)	$ (38,600,000)
Post May 2009 [Member] | Retirement Savings Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer Matching	3.00%
Minimum [Member] | Retirement Savings Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pre-tax compensation, percentage	2.00%
Maximum [Member] | Retirement Savings Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pre-tax compensation, percentage	50.00%