Segment Results (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Revenue		$ 153.7		$ 146.7		$ 304.4	$ 241.6
Operating profit		30.5		28.2		84.8	42.6
Interest expense		(6.6)		(7.2)		(13.7)	(14.5)
General corporate expenses		(5.3)		(4.3)		(10.9)	(9.5)
Reduction in KRS II carrying value		(1.5)		0.0		(1.6)	0.0
Income From Continuing Operations Before Income Taxes		17.1		16.7		58.6	18.6
Income tax expense		7.0		6.5		22.6	7.3
Income From Continuing Operations		10.1		10.2		36.0	11.3
Income From Discontinued Operations (net of income taxes)		0.0		0.0		0.0	34.3
Net Income		10.1		10.2		36.0	45.6
Income attributable to noncontrolling interest		(0.3)		(1.0)		(0.9)	(1.4)
Net Income Attributable to A&B Shareholders		9.8		9.2		35.1	44.2
Leasing
Segment Reporting Information [Line Items]
Revenue	[1]	34.8		31.0		67.5	62.2
Operating profit	[1]	13.9		12.0		27.1	23.8
Development and sales
Segment Reporting Information [Line Items]
Revenue	[1]	52.4		21.4		88.9	92.4
Operating profit	[1]	14.3		7.8		46.3	60.1
Less amounts reported in discontinued operations
Segment Reporting Information [Line Items]
Revenue	[1]	0.0		0.0		0.0	70.4
Operating profit	[1]	0.0		0.0		0.0	56.2
Materials and construction
Segment Reporting Information [Line Items]
Revenue		57.4		64.5		114.3	114.7
Operating profit		7.0		8.0		14.2	11.4
Agribusiness
Segment Reporting Information [Line Items]
Revenue		25.8		29.8		54.7	42.7
Operating profit		(4.7)		0.4		(2.8)	3.5
Reconciling item
Segment Reporting Information [Line Items]
Revenue		$ (16.7)	[2]	$ 0.0	[2]	$ (21.0)	$ 0.0

[1] Prior year amounts recast for amounts treated as discontinued operations.

[2] Represents the deduction of revenue from the sales of a Colorado retail property in March 2015 and a Texas office building in June 2015 that are classified as "Gain on the sale of improved property" in the Condensed Consolidated Statements of Income, but reflected as revenue for segment reporting purposes.