Segment Information - Segment Financial Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Net sales	$ 177,137	$ 182,374	$ 209,275	$ 190,245	$ 215,364	$ 176,780	$ 235,619	$ 177,493	$ 759,031	$ 805,256	$ 609,905
Operating income									95,655	136,443	55,925
Gross profit	40,370	33,187	65,735	44,444	62,821	34,257	72,086	53,854	183,736	223,018	138,625
Interest expense									4,237	6,658	7,427
Non-operating expense (income), net									(281)		(53)
Losses on extinguishment of debt										136	52
Provisions for income taxes									33,594	46,208	19,787
Equity in earnings of affiliate-Climate Control									(681)	(543)	(1,003)
Income from continuing operations	11,622	6,710	26,130	14,324	28,002	6,324	28,698	20,960	58,786	83,984	29,715
Chemical [Member]
Segment Reporting Information [Line Items]
Net sales									477,813	511,854	351,086
Operating income									82,101	116,503	31,948
Gross profit									97,692	130,687	49,295
Non-operating expense (income), net									(1)	(1)	(7)
Chemical [Member] | Agricultural products [Member]
Segment Reporting Information [Line Items]
Net sales									217,329	231,599	135,598
Chemical [Member] | Industrial acids and other chemical products [Member]
Segment Reporting Information [Line Items]
Net sales									162,498	161,776	126,846
Chemical [Member] | Mining products [Member]
Segment Reporting Information [Line Items]
Net sales									96,538	118,479	88,642
Chemical [Member] | Proved natural gas properties [Member]
Segment Reporting Information [Line Items]
Net sales									1,448
Climate Control [Member]
Segment Reporting Information [Line Items]
Net sales									266,171	281,565	250,521
Operating income									25,834	32,759	35,338
Gross profit									80,981	88,178	86,364
Non-operating expense (income), net									(1)	(2)	(3)
Climate Control [Member] | Geothermal and water source heat pumps [Member]
Segment Reporting Information [Line Items]
Net sales									162,697	183,789	171,561
Climate Control [Member] | Hydronic fan coils [Member]
Segment Reporting Information [Line Items]
Net sales									55,812	54,379	37,923
Climate Control [Member] | Other HVAC products [Member]
Segment Reporting Information [Line Items]
Net sales									47,662	43,397	41,037
Other [Member]
Segment Reporting Information [Line Items]
Net sales									15,047	11,837	8,298
Operating income									(12,280)	(12,819)	(11,361)
Gross profit									5,063	4,153	2,966
Non-operating expense (income), net									$ (279)	$ 3	$ (43)