Notes Payable, Other and Short-Term Borrowings - Carrying Amounts and Estimated Fair Values of Company's Senior Notes (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	$ 1,039,505	$ 742,517
Estimated fair value of the Company's long-term debt	1,081,065	756,195
5.125% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	298,469	297,821
Estimated fair value of the Company's long-term debt	309,540	304,890
5.375% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	444,925	444,696
Estimated fair value of the Company's long-term debt	470,025	$ 451,305
3.750% Senior Notes Due October 1, 2024 [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	296,111
Estimated fair value of the Company's long-term debt	$ 301,500