Retirement Benefit Arrangements (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure - Defined contribution plan
Incurred expense for defined contribution arrangements	$ 14,500,000	$ 15,700,000	$ 16,000,000
Zurich Plan
Funded status:
Unfunded pension obligation at beginning of year	32,262,000	25,162,000
Change in pension obligation:
Service cost	6,934,000	6,474,000
Interest cost	2,314,000	2,976,000
Plan participants' contributions	1,938,000	1,998,000
Actuarial (gain) loss	(8,408,000)	7,046,000
Plan amendments	0	(707,000)
Benefits paid	(216,000)	(8,582,000)
Foreign currency adjustments	2,901,000	4,349,000
Settlements	(13,783,000)	0
Change in pension obligation	(8,320,000)	13,554,000
Change in fair value of plan assets:
Actual return on plan assets	3,119,000	3,782,000
Employer contributions	5,922,000	5,941,000
Plan participants' contributions	1,938,000	1,998,000
Benefits paid	(216,000)	(8,582,000)
Foreign currency adjustments	2,348,000	3,315,000
Settlement	13,783,000	0
Change in fair value of plan assets	(672,000)	6,454,000
Funded status:
Unfunded pension obligation at end of year	24,614,000	32,262,000	25,162,000
Additional information:
Projected benefit obligation	126,390,000	134,710,000
Accumulated pension obligation	123,524,000	129,492,000
Fair value of plan assets	101,776,000	102,448,000
Defined Benefit Plan Estimated Future Benefit Payments Abstract
2014	4,417,000
2015	4,807,000
2016	5,046,000
2017	4,925,000
2018	4,722,000
2019 to 2023	$ 28,714,000
Pension obligation - assumptions used
Discount rate	2.25%	1.75%	2.50%
Rate of compensation increase	2.50%	2.50%	3.50%
Net periodic benefit cost - assumptions used
Discount Rate	1.75%	2.50%	2.75%
Return on plan assets	1.75%	2.50%	3.00%
Rate of Compensation increase	2.50%	3.50%	3.50%