Redemption Price of Notes Plus Accrued and Unpaid Interest Thereon to Redemption Date (Detail) - Senior Notes [Member]	12 Months Ended
	Dec. 31, 2015
5½% Senior Notes [Member] | 2017 [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	102.75%
5½% Senior Notes [Member] | 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	101.375%
5½% Senior Notes [Member] | 2019 and thereafter [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	100.00%
5% Senior Notes due 2020 [Member] | 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	102.50%
5% Senior Notes due 2020 [Member] | 2017 [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	101.25%
5% Senior Notes due 2020 [Member] | 2018 and thereafter [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	100.00%