Long Term Debt Outstanding (Detail) - USD ($) $ in Thousands		Jun. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Long-term debt	[1]	$ 3,196,847	$ 3,183,140
7.456% Senior Notes Due 2018
Debt Instrument [Line Items]
Long-term debt		500,000	500,000
5.95% Senior Notes Due 2020
Debt Instrument [Line Items]
Long-term debt		746,618	746,216
4.5% Senior Notes Due 2024
Debt Instrument [Line Items]
Long-term debt		494,133	493,797
2.5% Senior Notes Due 2022
Debt Instrument [Line Items]
Long-term debt		716,027	703,254
5.0% Senior Notes Due 2026
Debt Instrument [Line Items]
Long-term debt		$ 740,069	$ 739,873

[1] Net of applicable discounts and debt issuance costs.