Notes Payable, Other and Short-term Borrowings - Carrying Amounts and Estimated Fair Values of Company's Senior Notes (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	$ 1,040,862	$ 946,930
Estimated fair value of the Company's long-term debt	1,060,031	992,250
8.125% Senior Notes Due 2042 [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt		109,396
Estimated fair value of the Company's long-term debt		116,550
5.375% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	298,801	298,064
Estimated fair value of the Company's long-term debt	305,040	313,125
8.375% Senior Notes Due July 2018 [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt		242,474
Estimated fair value of the Company's long-term debt		247,200
5.125% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	297,611	296,996
Estimated fair value of the Company's long-term debt	305,895	$ 315,375
5.375% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	444,450
Estimated fair value of the Company's long-term debt	$ 449,096