Indebtedness - Debt Outstanding (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Total debt	$ 2,999,000	$ 3,140,516
Notes Payable to Banks | 2.2% Bank Debt
Debt Instrument [Line Items]
Total debt	649,000	500,000
Senior Subordinated Notes | 8.00% Notes Due 2019
Debt Instrument [Line Items]
Total debt		290,516
Senior Subordinated Notes | 6.75% Notes Due 2020
Debt Instrument [Line Items]
Total debt	500,000	500,000
Senior Subordinated Notes | 5.75% Notes Due 2021
Debt Instrument [Line Items]
Total debt	500,000	500,000
Senior Subordinated Notes | 5.00% Notes Due 2022
Debt Instrument [Line Items]
Total debt	600,000	600,000
Senior Subordinated Notes | 5.00% Notes Due 2023
Debt Instrument [Line Items]
Total debt	$ 750,000	$ 750,000