SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Summary of Changes in Fair Value Level 2 Assets (Liabilities) of Derivative Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013
Balance at beginning of period	$ 3,524	$ 11,651
Purchases and settlements (net)	3,560	(1,641)
Realized gains (losses) included in other income (expenses)	(3,560)	1,641
Unrealized gains (losses) included in other income (expenses)	(3,835)	(11,962)
Balance at end of period	$ (311)	$ (311)