Summary of Significant Accounting Policies (Details)	1 Months Ended
	Dec. 31, 2011 company	Jun. 30, 2012 state
Basis of Presentation
Number of small manufacturing companies owned by the Tuckerman Fund I from whom the entity received shares	2
Number of states in which Esurance insurance directly writes insurance		30
OneBeacon Ltd.
Basis of Presentation
Ownership percentage in outstanding common shares	75.50%	75.20%