Commitments And Contingencies (Other Contingencies) (Detail) (USD $)			3 Months Ended								12 Months Ended
	Mar. 31, 2013	Mar. 31, 2007	Dec. 31, 2011 Environmental Claims For A Site In Goodyear Arizona	Dec. 31, 2008 Environmental Claims For A Site In Goodyear Arizona	Mar. 31, 2013 Environmental Claims For A Site In Goodyear Arizona	Dec. 31, 2007 Environmental Claims For A Site In Goodyear Arizona	Jul. 31, 2006 Environmental Claims For A Site In Goodyear Arizona	Mar. 31, 2013 Environmental Claims For Crab Orchard National Wildlife Refuge Superfund Site acre	Mar. 31, 2013 Site 36 [Member]	Jan. 08, 2010 Merrimac Securities Class Action Lawsuit	Dec. 31, 2011 Environmental Claims For Site In Roseland New Jersey Home	Dec. 31, 2011 Environmental Claims For Site In Roseland New Jersey Homeowner	Apr. 15, 2011 Environmental Claims For Site In Roseland New Jersey Home	Jan. 11, 2013 Subsequent Event [Member]
Loss Contingencies [Line Items]
Estimated liability				$ 65,200,000	$ 46,300,000	$ 41,500,000
Amount of additional remediation activities			30,300,000	24,300,000
Accrued environmental loss contingencies current					16,000,000
Loss contingency reimbursement rate							21.00%
Other receivables					10,900,000
Approximate size of referenced site, acres								55,000
Amount_to_resolve_all_past_and_future_claims_for_response_costs									166,667
Stock price per share										$ 16.00
Approximate number of homes tested for contaminants											40	40
Number of Homes Where Contaminants Were Found											3	3
Number of tenants who filed a separate lawsuit													1
Number of members in the purported class											141	141
Airplane operating lease period, years		7 years
Fair value of residual value guarantee	6,200,000	14,100,000
Operating lease, fair value, commitment		22,100,000
Settlement Fund														2,000,000
Contribution by Company to Settlement Fund														$ 150,000