Components of Debt Obligations (Parenthetical) (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
6 3/4 % Senior Notes Due 2020
Debt Instrument [Line Items]
Interest percentage	6.75%	6.75%
Debt maturity period	2020	2020
6.0% Senior Notes Due 2022
Debt Instrument [Line Items]
Interest percentage	6.00%	6.00%
Debt maturity period	2022	2022