Notes Payable, Other and Short-Term Borrowings - Summary Notes Payable, Other and Short-term Borrowings (Parenthetical) (Detail)	Mar. 31, 2019	Dec. 31, 2018	Nov. 23, 2018	Jul. 24, 2018	May 27, 2016
8.375% Senior Notes Due July 2018 [Member]
Debt Instrument [Line Items]
Stated interest rate	8.375%	8.375%
5.125% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Stated interest rate	5.125%	5.125%			5.125%
5.375% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Stated interest rate	5.375%	5.375%	5.375%
5.375% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Stated interest rate	5.375%	5.375%		5.375%