Equity Method Investments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Equity method investments
Investments in and advances to affiliates	$ 934.7		$ 928.6
Condensed income statement information:
Equity in earnings of operating affiliates	15.5	11.5
Equity in earnings of non-operating affiliates-net of taxes	(2.3)	8.5
Operating Equity Method Investments
Equity method investments
Investments in and advances to affiliates	407.9		413.1
Condensed income statement information:
Net sales	77.5	79.8
Net earnings	24.5	27.5
Equity in earnings of operating affiliates	15.5	11.5
Condensed balance sheet information:
Current assets	105.1		126.6
Long-term assets	147.4		147.2
Total assets	252.5		273.8
Current liabilities	30.5		41.1
Long-term liabilities	20.0		24.2
Equity	202.0		208.5
Total liabilities and equity	252.5		273.8
Equity Method Investments
Carrying value of investments	407.9
Carrying value of investments in excess of the entity's share of the affiliates' book value	306.9
Operating Equity Method Investments | Maximum
Equity Method Investments
Number of years that the increased basis for property, plant and equipment and identifiable intangibles will be depreciated	12
Operating Equity Method Investments | Minimum
Equity Method Investments
Number of years that the increased basis for property, plant and equipment and identifiable intangibles will be depreciated	22
Operating Equity Method Investments | Point Lisas Nitrogen Limited (PLNL)
Equity method investments
Ownership interest (as a percent)	50.00%
Equity Method Investments
Obligation to purchase ammonia (as a percent)	50% of ammonia produced by PLNL
Purchases of ammonia from PLNL since date acquisition	38.5	36.0
Operating Equity Method Investments | Ammonia storage joint venture
Equity method investments
Ownership interest (as a percent)	50.00%
Non-Operating Equity Method Investments
Equity method investments
Investments in and advances to affiliates	526.8		515.5
Condensed income statement information:
Net sales	638.4	530.3
Net earnings	2.0	23.2
Equity in earnings of non-operating affiliates-net of taxes	(2.3)	8.5
Condensed balance sheet information:
Current assets	519.1		504.2
Long-term assets	295.7		293.4
Total assets	814.8		797.6
Current liabilities	349.7		339.5
Long-term liabilities	148.5		149.4
Equity	316.6		308.7
Total liabilities and equity	814.8		797.6
Equity Method Investments
Amount of consolidated retained earnings	16.5
Non-Operating Equity Method Investments | KEYTRADE AG
Equity method investments
Ownership interest (as a percent)	50.00%
Equity Method Investments
Carrying value of investments	514.4
Carrying value of investments in excess of the entity's share of the affiliates' book value	356.1
Percentage on debt instrument in addition to LIBOR Rate	1.00%
Amount of outstanding advances	12.4		12.4
Recognized interest income on advances	$ 0.1	$ 0.1
Non-Operating Equity Method Investments | KEYTRADE AG | Maximum
Equity Method Investments
Number of years that the increased basis for property, plant and equipment and identifiable intangibles will be depreciated	14
Non-Operating Equity Method Investments | KEYTRADE AG | Minimum
Equity Method Investments
Number of years that the increased basis for property, plant and equipment and identifiable intangibles will be depreciated	2
Non-Operating Equity Method Investments | GrowHow
Equity method investments
Ownership interest (as a percent)	50.00%