CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (USD $)	Total	Common shares and paid-in surplus	Retained earnings	Accum. other comprehensive income (loss)	Total OneBeacon common shareholders' equity	Noncontrolling interests, after tax
Balances at Dec. 31, 2012	$ 1,017,300,000	$ 1,019,100,000	$ 9,200,000	$ (13,800,000)	$ 1,014,500,000	$ 2,800,000
Increase (Decrease) in Stockholders' Equity
Net income	68,800,000	0	68,400,000	0	68,400,000	400,000
Net change in benefit plan assets and obligations, net of tax	100,000	0	0	100,000	100,000	0
Total comprehensive income	68,900,000	0	68,400,000	100,000	68,500,000	400,000
Amortization of restricted share awards	800,000	800,000	0	0	800,000	0
Issuance of common shares	100,000	0	0	0	0	100,000
Dividends	(20,800,000)	0	(20,000,000)	0	(20,000,000)	(800,000)
Balances at Mar. 31, 2013	1,066,300,000	1,019,900,000	57,600,000	(13,700,000)	1,063,800,000	2,500,000
Balances at Dec. 31, 2013	1,107,400,000				1,104,300,000
Common Stocks, Including Additional Paid in Capital	1,021,500,000
Retained earnings	102,000,000
Accumulated other comprehensive loss, after tax	6,800,000
Total noncontrolling interests, after tax	2,800,000
Increase (Decrease) in Stockholders' Equity
Net income	47,400,000	0	47,000,000	0	47,000,000	400,000
Net change in benefit plan assets and obligations, net of tax	0	0	0	0	0	0
Total comprehensive income	47,400,000	0	47,000,000	0	47,000,000	400,000
Amortization of restricted share awards	800,000	800,000	0	0	800,000	0
Issuance of common shares	200,000	0	0	0	0	200,000
Repurchase and retirement of common shares	(1,800,000)	(1,800,000)	0	0	(1,800,000)	0
Dividends	(20,900,000)	0	(20,000,000)	0	(20,000,000)	(900,000)
Balances at Mar. 31, 2014	$ 1,133,100,000	$ 1,021,500,000	$ 102,000,000	$ 6,800,000	$ 1,130,300,000	$ 2,800,000