Financing Agreements (Details) (USD $)					3 Months Ended		3 Months Ended							12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 CFI	Dec. 31, 2011 CFI	Mar. 31, 2012 CFI Credit Agreement	Mar. 31, 2012 CFI Revolving credit facility	Mar. 31, 2012 CFI Senior notes due 2018 and 2020	Mar. 31, 2012 CFI Unsecured senior notes 6.875% due 2018	Dec. 31, 2011 CFI Unsecured senior notes 6.875% due 2018	Apr. 23, 2010 CFI Unsecured senior notes 6.875% due 2018	Mar. 31, 2012 CFI Unsecured senior notes 7.125% due 2020	Dec. 31, 2011 CFI Unsecured senior notes 7.125% due 2020	Apr. 23, 2010 CFI Unsecured senior notes 7.125% due 2020	Dec. 31, 2009 Terra Unsecured senior notes 7.0% due 2017	Mar. 31, 2012 Terra Unsecured senior notes 7.0% due 2017	Dec. 31, 2011 Terra Unsecured senior notes 7.0% due 2017	Dec. 31, 2007 Terra Unsecured senior notes 7.0% due 2017
Financing agreements
Long-term debt	$ 1,613,000,000	$ 1,613,000,000					$ 1,600,000,000	$ 800,000,000	$ 800,000,000		$ 800,000,000	$ 800,000,000			$ 13,000,000	$ 13,000,000
Net long-term debt	1,613,000,000	1,613,000,000	1,600,000,000	1,600,000,000
Debt Instruments
Maximum borrowing capacity						500,000,000
Interest rate (as a percent)								6.875%			7.125%				7.00%
Principal amount										800,000,000			800,000,000				330,000,000
Variable interest base rate					applicable margin over LIBOR or a base rate
Available credit						491,200,000
Repayment of borrowings														317,500,000
Carrying value of long term debt	1,613,000,000	1,613,000,000					1,600,000,000	800,000,000	800,000,000		800,000,000	800,000,000			13,000,000	13,000,000
Fair value of long-term debt							$ 1,900,000,000
Repurchase price of notes as a percentage of principal amount							101.00%