Schedule I - Condensed Financial Information of Registrant - Summary of Transactions Related to Debentures (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Feb. 01, 2013
Condensed Financial Information Of Registrant [Line Items]
Principal amounts converted or acquired		$ 26,900,000	$ 2,500,000	$ 35,000,000
Cash paid for acquisitions			2,494,000
Shares of LSB common stock issued		979,160
Parent company [Member]
Condensed Financial Information Of Registrant [Line Items]
Principal amounts converted or acquired		26,900,000	2,500,000
Cash paid for acquisitions			$ 2,494,000
Shares of LSB common stock issued		979,160