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Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended			3 Months Ended
	Dec. 31, 2014 Reportable_Segment	Dec. 31, 2013	Dec. 31, 2012 Operation	Mar. 31, 2015	Feb. 03, 2006 Defined_Benefit_Plan
Accounting Policies [Line Items]
Number of principal reporting segments	3us-gaap_NumberOfReportableSegments
Outstanding forward exchange contracts related to sales	$ 2,527,000invest_DerivativeNotionalAmount
Goodwill, Balance at the beginning of the period	32,073,000us-gaap_Goodwill	31,648,000us-gaap_Goodwill	31,751,000us-gaap_Goodwill
Goodwill percentage of total assets	12.00%alg_GoodwillAsPercentageOfTotalAssets
Goodwill impairment	0us-gaap_GoodwillImpairmentLoss	0us-gaap_GoodwillImpairmentLoss	656,000us-gaap_GoodwillImpairmentLoss
Number of operations			1
Hypothetical percentage decline in fair value of each reporting unit	15.00%
Net book value of assets	51,484,000us-gaap_FiniteLivedIntangibleAssetsNet	0us-gaap_FiniteLivedIntangibleAssetsNet
Number of defined benefit pension plans					2alg_NumberOfDefinedBenefitPensionPlans
Accumulated depreciation relating to rental equipment	100,497,000	96,472,000
Book value of capitalized software	1,370,000us-gaap_CapitalizedComputerSoftwareNet	944,000us-gaap_CapitalizedComputerSoftwareNet
Option term (years)	10 years
Options
Accounting Policies [Line Items]
Award vesting period (years)	5 years
Low
Accounting Policies [Line Items]
Estimated Useful Lives	12 years
High
Accounting Policies [Line Items]
Estimated Useful Lives	25 years
Period of lease agreement	2 years
Rental Equipment
Accounting Policies [Line Items]
Accumulated depreciation relating to rental equipment	3,435,000
Software Development
Accounting Policies [Line Items]
Software depreciation	556,000	488,000	676,000
Software Development \| Low
Accounting Policies [Line Items]
Useful Lives	3 years
Software Development \| High
Accounting Policies [Line Items]
Useful Lives	7 years
Hourly Employees’ Pension Plan
Accounting Policies [Line Items]
Former employees	331
Current employees	125
Employees’ Retirement Plan
Accounting Policies [Line Items]
Former employees	238
Current employees	83
Trade Names
Accounting Policies [Line Items]
Indefinite:	5,500,000	5,500,000
Trade Names \| Gradall
Accounting Policies [Line Items]
Indefinite:	3,600,000
Trade Names \| Bush Hog
Accounting Policies [Line Items]
Indefinite:	1,900,000
Other income (expense)
Accounting Policies [Line Items]
Foreign currency transaction gains	503,000	921,000	(476,000)
Selling, General and Administrative expenses
Accounting Policies [Line Items]
Advertising expense	7,368,000	6,646,000	6,353,000
Product development and engineering costs	8,427,000	7,164,000	5,686,000
Scenario, Forecast
Accounting Policies [Line Items]
Unrealized gain of contracts				(27,000)
Correction of Misclassification of Freight Revenue
Accounting Policies [Line Items]
Increase in sales and cost of sales		5,300,000	4,600,000
Freight allowances	$ 5,500,000