Derivatives and Fair Value Measurements - Gains (Losses) Recognized in Other Comprehensive Income for Derivatives as Cash Flow Hedging Instruments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Offsetting [Abstract]
Amount of gain/(loss) realized/ unrealized on FSIRS recognized in other comprehensive income on derivative				$ 2,959		$ 1,383