Segment Results - Operating Segment Information (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended																		12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Sep. 30, 2012 acre	Jun. 30, 2012	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue	$ 165.1		$ 153.4		$ 146.7		$ 94.8		$ 204.8		$ 64.9		$ 62.7		$ 32.8				$ 560.0		$ 365.2		$ 261.5
Operating profit (loss)	26.5		22.1		28.2		14.3		35.2		6.2		14.4		8.9				91.1		64.7		36.9
Interest expense	(7.4)		(7.2)		(7.2)		(7.2)		(7.4)		(4.2)		(3.9)		(3.6)				(29.0)		(19.1)		(14.9)
General corporate expenses	(5.2)		(3.9)		(4.3)		(5.2)		(5.9)		(3.4)		(3.7)		(4.4)				(18.6)		(17.4)		(15.1)
Reduction in KRS II carrying value, net (Note 6, 13)	0.4		(15.1)		0		0												(14.7)		0		0
Separation/Acquisition Costs									(0.1)		(2.0)		(1.5)		(1.0)				0		(4.6)		(6.8)
Income From Continuing Operations Before Income Taxes	14.3		(4.1)		16.7		1.9		21.8		(3.4)		5.3		(0.1)				28.8		23.6		0.1
Income tax expense (benefit)	6.2		(14.9)		6.5		0.8		8.5		(0.3)		2.8		0.1				(1.4)		11.1		(5.9)
Income From Continuing Operations	8.1		10.8		10.2		1.1		13.3		(3.1)		2.5		(0.2)				30.2		12.5		6.0
Income from discontinued operations (net of income taxes)	0		0		0		34.3		7.8		7.2		2.3		5.0				34.3		22.3		12.8
Net Income	8.1		10.8		10.2		35.4		21.1		4.1		4.8		4.8				64.5		34.8		18.8
Income attributable to non-controlling interest	(1.1)		(0.6)		(1.0)		(0.4)		(0.5)		0		0		0				(3.1)		(0.5)		0
Net Income Attributable to A&B	7.0		10.2		9.2		35.0		20.6		4.1		4.8		4.8				61.4		34.3		18.8
Area of agricultural parcel sold																	286
Income (loss) related to joint ventures																			2.1		4.3		(4.4)
Impairment of real estate assets																		5.1	0		0		5.1
Earnings Per Share, Basic (USD per share)	$ 0.14		$ 0.21		$ 0.19		$ 0.72		$ 0.42		$ 0.10		$ 0.11		$ 0.11				$ 1.26		$ 0.77		$ 0.44
Earnings Per Share, Diluted (USD per share)	$ 0.14		$ 0.21		$ 0.19		$ 0.71		$ 0.42		$ 0.09		$ 0.11		$ 0.11				$ 1.25		$ 0.76		$ 0.44
Basic (in shares)	48.8		48.8		48.7		48.7		48.6		43.1		43.1		43.0				48.7		44.4		42.6
Diluted (in shares)	49.3		49.3		49.3		49.2		49.2		43.8		43.7		43.6				49.3		45.1		42.9
The effect to current period income tax expense and net income due to out of period adjustment							1.6
Segment Reporting Information, Additional Information [Abstract]
Assets	2,329.9								2,283.6										2,329.9		2,283.6		1,437.3
Total capital expenditures																			75.1		505.3		54.8
Depreciation and amortization																			55.0		41.7		35.1
Capital before tax credits related to Port Allen solar project																							21.8
Real Estate Leasing
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue	32.1		31.3		31.0		31.2		30.4		27.5		26.2		26.3				125.6		110.4		100.6
Operating profit (loss)	11.6		12.1		12.0		11.8		10.7		11.2		10.6		10.9				47.5		43.4		41.6
Segment Reporting Information, Additional Information [Abstract]
Assets	1,121.6								1,113.4										1,121.6		1,113.4		771.3
Total capital expenditures																			51.8	[1]	488.5	[1]	23.1	[1]
Depreciation and amortization																			26.9	[2]	24.3	[2]	22.0	[2]
Real Estate Development and Sales
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue	39.4		18.2		21.4		71.0		358.8		47.4		1.4		15.4				150.0		423.0		32.2
Operating profit (loss)	14.2	[3]	11.4	[3]	7.8	[3]	52.3	[3]	38.1	[3]	4.6	[3]	(0.7)	[3]	2.4	[3]			85.7	[4]	44.4	[4]	(4.4)	[4]
Income (loss) related to joint ventures																			2.0		4.2		(8.3)
Impairment of real estate assets											6.3
Segment Reporting Information, Additional Information [Abstract]
Assets	634.3	[5]							640.9	[5]									634.3	[5]	640.9	[5]	504.8	[5]
Total capital expenditures																			0	[6]	0.1	[6]	0	[6]
Depreciation and amortization																			0.2		0.2		0.2
Investment in various real estate joint ventures	383.8								335.0										383.8		335.0		319.7
Expenditures for real estate inventory																			41.7		150.6		37.2
Investment in joint ventures																			28.7		22.2		17.4
Less amounts reported in discontinued operations
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue	0	[2]	0	[2]	0	[2]	70.4	[2]	291.3	[2]	45.9	[2]	8.4	[2]	23.6	[2]			70.4	[2]	369.2	[2]	45.3	[2]
Operating profit (loss)	0	[2]	0	[2]	0	[2]	56.2	[2]	12.9	[2]	11.8	[2]	3.8	[2]	8.2	[2]			56.2	[2]	36.7	[2]	21.1	[2]
Materials & Construction
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue	61.3		58.4		64.5		50.1		54.9	[7]	0	[7]	0	[7]	0	[7]			234.3	[8]	54.9	[8]	0	[8]
Operating profit (loss)	8.6		5.9		8.0		3.4		2.9		0		0		0				25.9	[8]	2.9	[8]	0	[8]
Segment Reporting Information, Additional Information [Abstract]
Assets	385.9								358.7										385.9		358.7		0
Total capital expenditures																			10.7	[8]	4.8	[8]	0	[8]
Depreciation and amortization																			15.2	[8]	4.4	[8]	0	[8]
Agribusiness
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue	32.3		45.5		29.8		12.9		52.0		35.9		43.5		14.7				120.5		146.1		182.3
Operating profit (loss)	(7.9)		(7.3)		0.4		3.0		(3.6)		2.2		8.3		3.8				(11.8)		10.7		20.8
Segment Reporting Information, Additional Information [Abstract]
Assets	162.8								160.0										162.8		160.0		149.9
Total capital expenditures																			10.8	[9]	11.8	[9]	31.7	[9]
Depreciation and amortization																			11.5		11.7		11.6
Significant Reconciling Items
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue																			0	[10]	0	[10]	(8.3)	[10]
Other
Segment Reporting Information, Additional Information [Abstract]
Assets	25.3								10.6										25.3		10.6		11.3
Total capital expenditures																			1.8		0.1		0
Depreciation and amortization																			1.2		1.1		1.3
Crossroads | Real Estate Development and Sales
Segment Reporting Information, Profit (Loss) [Abstract]
Impairment of real estate assets																			0.3
Kukui'ula Village LLC | Real Estate Development and Sales
Segment Reporting Information, Profit (Loss) [Abstract]
Impairment of real estate assets																					6.3
Bakersfield and Santa Barbara Real Estate Projects | Real Estate Development and Sales
Segment Reporting Information, Profit (Loss) [Abstract]
Impairment of real estate assets																							9.8
Restatement Adjustment | Out of Period Tax Adjustments
Segment Reporting Information, Profit (Loss) [Abstract]
Income tax expense (benefit)									$ 1.9		$ 0.3		$ 0.2		$ 0.2						$ 2.6		$ 1.7

[1] Represents gross capital additions to the leasing portfolio, including gross tax-deferred property purchases, but excluding the assumption of debt, that are reflected as non-cash transactions in the Consolidated Statements of Cash Flows.

[2] Amounts recast to reflect discontinued operations

[3] The Real Estate Development and Sales segment operating profit includes a non-cash impairment loss of $6.3 million in the third quarter of 2013 related to the consolidation of The Shops at Kukui'ula.

[4] The Real Estate Development and Sales segment includes approximately $2.0 million, $4.2 million, and ($8.3) million in equity in earnings (losses) from its various real estate joint ventures for 2014, 2013, and 2012, respectively. Included in operating profit are non-cash impairment and equity losses of $0.3 million related to the sale of Crossroads in 2014, $6.3 million related to the consolidation of The Shops at Kukui'ula in 2013, and $9.8 million related to the Bakersfield joint venture and Santa Barbara real estate project in 2012.

[5] The Real Estate Development and Sales segment includes approximately $383.8 million, $335.0 million, and $319.7 million related to its investment in various real estate joint ventures as of December 31, 2014, 2013, and 2012, respectively.

[6] Excludes expenditures for real estate developments held for sale which are classified as Cash Flows from Operating Activities within the Consolidated Statements of Cash Flows and excludes investment in joint ventures classified as Cash Flows from Investing Activities. Operating cash flows for expenditures related to real estate developments were $41.7 million, $150.6 million, and $37.2 million for 2014, 2013, and 2012, respectively. Investments in real estate joint ventures were $28.7 million, $22.2 million, and $17.4 million in 2014, 2013, and 2012, respectively.

[7] Income tax expense (benefit) for the first quarter of 2014 was revised to remove an out-of-period tax adjustment of $1.6 million related to 2013. Income tax expense (benefit) for the quarterly periods in 2013 were increased by $0.2 million, $0.2 million, $0.3 million, and $1.9 million related to the immaterial revisions (see Note 1).

[8] 2013 includes the results, capital expenditures, and depreciation and amortization of Grace from the acquisition date of October 1, 2013 through December 31, 2013.

[9] Includes $21.8 million of capital in 2012 related to the Company’s Port Allen solar project before tax credits.

[10] Represents the sale of a 286-acre agricultural parcel in 2012 classified as "Gain on sale of agricultural parcel" in the Consolidated Statements of Income, but reflected as revenue for segment reporting purposes.