Revolving Line of Credit - Chronology of Total Commitment Under Revolving Credit Facility with Associated Rate Options in Effect (Detail) (USD $) In Millions, unless otherwise specified	10 Months Ended	12 Months Ended
	Oct. 31, 2011	Dec. 31, 2012	Sep. 30, 2013	Aug. 02, 2007
Debt Disclosure [Abstract]
Amendment Date	Oct. 31, 2011	Dec. 31, 2012
Total Commitment under Credit Facility	$ 100	$ 150	$ 150	$ 30
Rate options	Prime plus 0.75% or LIBOR plus 2.75%	Base plus 0.75% or LIBOR plus 2.50%