Notes Payable, Collateralized and Short-Term Borrowings - Notes Payable, Collateralized and Short-Term Borrowings (Parenthetical) (Detail)	Dec. 31, 2016	Jul. 15, 2016	Jul. 13, 2016	May 27, 2016	Dec. 31, 2015	Dec. 09, 2014	Jul. 29, 2011
4.50% Convertible Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	4.50%	4.50%	4.50%		4.50%		4.50%
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%