Indebtedness - Debt Outstanding (Parenthetical) (Detail)	Jun. 30, 2015	May. 31, 2015	Dec. 31, 2014
Notes Payable to Banks | 1.5% Bank Debt
Debt Instrument [Line Items]
Bank debt percentage	1.50%		1.50%
Senior Notes | 4.875% Senior Notes Due 2025
Debt Instrument [Line Items]
Interest rate on notes	4.875%	4.875%	4.875%
Senior Subordinated Notes | 4.875% Senior Notes Due 2025
Debt Instrument [Line Items]
Interest rate on notes	4.875%		4.875%
Senior Subordinated Notes | 6.75% Senior Subordinated Notes Due 2020
Debt Instrument [Line Items]
Interest rate on notes	6.75%	6.75%	6.75%
Senior Subordinated Notes | 5.75% Senior Subordinated Notes Due 2021
Debt Instrument [Line Items]
Interest rate on notes	5.75%		5.75%
Senior Subordinated Notes | 5.00% Senior Subordinated Notes Due 2022
Debt Instrument [Line Items]
Interest rate on notes	5.00%		5.00%
Senior Subordinated Notes | 5.00% Senior Subordinated Notes Due 2023
Debt Instrument [Line Items]
Interest rate on notes	5.00%		5.00%