Common stock (Tables)

12 Months Ended

Dec. 31, 2012

Changes in issued and outstanding Berkshire common stock

Changes in Berkshire’s issued and outstanding common stock during the three years ending December 31, 2012 are shown in the table below.

	Class A, $5 Par Value (1,650,000 shares authorized)									Class B, $0.0033 Par Value (3,225,000,000 shares  authorized)
	Issued			Treasury			Outstanding			Issued		Treasury			Outstanding
Balance at December 31, 2009		1,055,281			—			1,055,281			744,701,300		—			744,701,300
Shares issued in the acquisition of BNSF		80,931			—			80,931			20,976,621		—			20,976,621
Conversions of Class A common stock to Class B common stock and exercises of replacement stock options issued in a business acquisition		(188,752	)		—			(188,752	)		285,312,547		—			285,312,547
Balance at December 31, 2010		947,460			—			947,460			1,050,990,468		—			1,050,990,468
Shares issued to acquire noncontrolling interests of Wesco Financial Corporation		—			—			—			3,253,472		—			3,253,472
Conversions of Class A common stock to Class B common stock and exercises of replacement stock options issued in a business acquisition		(9,118	)		—			(9,118	)		15,401,421		—			15,401,421
Treasury shares acquired		—			(98	)		(98	)		—		(801,985	)		(801,985	)
Balance at December 31, 2011		938,342			(98	)		938,244			1,069,645,361		(801,985	)		1,068,843,376
Conversions of Class A common stock to Class B common stock and exercises of replacement stock options issued in a business acquisition		(33,814	)		—			(33,814	)		53,748,595		—			53,748,595
Treasury shares acquired		—			(9,475	)		(9,475	)		—		(606,499	)		(606,499	)
Balance at December 31, 2012		904,528			(9,573	)		894,955			1,123,393,956		(1,408,484	)		1,121,985,472