Equity and Other Investments - Schedule of Combined Financial Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Net income	$ 36,126	$ 52,001	$ 125,097	$ 153,248
Current assets	139,145		139,145		196,195
Property, plant and equipment	27,703		27,703		32,401
Other assets	527		527		630
Total assets	1,950,635		1,950,635		1,764,672
Current liabilities	83,249		83,249		117,815
Long term debt	1,088,884		1,088,884		897,039
Capital	632,844		632,844		617,447
Total liabilities and partners' capital	1,950,635		1,950,635		1,764,672
Excess of NRP's investment over net book value of NRP's equity interests	78,700		78,700
OCI LP and OCI Co [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Net sales	105,567		324,559
Gross profit	20,545		63,860
Net income	16,323		53,281
Income allocation to NRP's equity interests	7,951		24,113
Current assets	172,318		172,318
Property, plant and equipment	192,395		192,395
Other assets	1,319		1,319
Total assets	366,032		366,032
Current liabilities	36,167		36,167
Long term debt	155,000		155,000
Other liabilities	3,716		3,716
Capital	171,149		171,149
Total liabilities and partners' capital	366,032		366,032
Net book value of NRP's equity interests	83,863		83,863
Excess of NRP's investment over net book value of NRP's equity interests	$ 158,544		$ 158,544