Industry Segments (Narrative) (Details)	3 Months Ended
	Mar. 31, 2012 countries segment
Number Of Operating Segments	5
Number of Countries International Operating Units Write Business	40
Specialty Segment [Member]
Number Of Operating Units	20
Regional Segment [Member]
Number of state of providing commercial insurance to customer	45
International Segment [Member]
Number Of Branches Or Offices Outside United States	15