Notes Payable, Other and Short-Term Borrowings - Carrying Amounts and Estimated Fair Values of Company's Senior Notes (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	$ 742,467	$ 742,517
Estimated fair value of the Company's long-term debt	770,610	756,195
5.125% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	298,034	297,821
Estimated fair value of the Company's long-term debt	306,840	304,890
5.375% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	444,433	444,696
Estimated fair value of the Company's long-term debt	$ 463,770	$ 451,305