Notes Payable, Collateralized and Short-Term Borrowings - Notes Payable, Collateralized and Short-Term Borrowings (Parenthetical) (Detail)	Mar. 31, 2017	Dec. 31, 2016	May 27, 2016	Dec. 09, 2014
8.125% Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	8.125%	8.125%
5.375% Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	5.375%	5.375%		5.375%
8.375% Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	8.375%	8.375%
5.125% Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	5.125%	5.125%	5.125%