Long-Term Debt - Summary of Acquisition Transactions (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Feb. 01, 2013
Debt Instrument [Line Items]
Principal amounts converted or acquired		$ 26,900	$ 2,500	$ 35,000
Cash paid for acquisitions			$ 2,494
Shares of LSB common stock issued		979,160