Segment Information (Details 5) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
US Segment Reporting Information [Member]
Premium Concentration [Line Items]
Gross Premiums From Five Largests Clients	$ 1,511,414,000	$ 1,401,487,000
Percentage Of Gross Premiums From Five Largests Clients	33.40%	33.50%
Canada Segment Reporting Information [Member]
Premium Concentration [Line Items]
Gross Premiums From Five Largests Clients	513,945,000	503,472,000
Percentage Of Gross Premiums From Five Largests Clients	53.10%	53.60%
Europe And South Africa Segment Reporting Information [Member]
Premium Concentration [Line Items]
Gross Premiums From Five Largests Clients	671,511,000	634,156,000
Percentage Of Gross Premiums From Five Largests Clients	50.20%	51.80%
Asia Pacific Segment Reporting Information [Member]
Premium Concentration [Line Items]
Gross Premiums From Five Largests Clients	550,975,000	603,541,000
Percentage Of Gross Premiums From Five Largests Clients	39.60%	45.00%
Corporate And Other Segment Reporting Information [Member]
Premium Concentration [Line Items]
Gross Premiums From Five Largests Clients	$ 1,913,475,000	$ 1,887,095,000
Percentage Of Gross Premiums From Five Largests Clients	23.20%	24.50%