Background and Basis of Presentation (Details) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended								12 Months Ended
	Jun. 18, 2012	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014 Segment	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Number of shares of AB common stock received	1
Number of operating segments										4
Other noncurrent assets		$ 43.5				$ 75.9				$ 43.5	$ 75.9
Adjustment of an understatement of net income taxes		6.2	(14.9)	6.5	0.8	8.5	(0.3)	2.8	0.1	(1.4)	11.1	(5.9)
Adjustment to overstated comprehensive income attributable to A&B										47.1	51.4	19.2
The effect to current period income tax expense and net income due to out of period adjustment					1.6
Adjustment to overstated non-current deferred tax liability		194.0				193.2				194.0	193.2
Adjustment to overstated income tax receivable		6.7				1.4				6.7	1.4
Adjustment to overstated net investments		418.6				341.4				418.6	341.4
Real Estate Leasing
Segment Reporting Information [Line Items]
Number of operating segments										1
Materials & Construction
Segment Reporting Information [Line Items]
Number of operating segments										1
Real Estate Development and Sales
Segment Reporting Information [Line Items]
Number of operating segments										1
Agribusiness
Segment Reporting Information [Line Items]
Number of operating segments										1
Out of Period Tax Adjustments | Restatement Adjustment
Segment Reporting Information [Line Items]
Adjustment to overstated net income attributable to A&B											(2.6)	(1.7)
Adjustment of an understatement of net income taxes						1.9	0.3	0.2	0.2		2.6	1.7
Adjustment to overstated comprehensive income attributable to A&B											(2.6)	(1.7)
Adjustment to overstated non-current deferred tax liability						(0.6)					(0.6)	(1.5)
Adjustment to overstated current deferred tax liability												(0.2)
Adjustment to overstated income tax receivable						(2.0)					(2.0)
Adjustment to overstated net investments												$ (1.8)