Notes Payable, Collateralized and Short-Term Borrowings - Carrying Amounts and Estimated Fair Values of Company's Convertible Notes and Senior Notes (Parenthetical) (Detail)	Mar. 31, 2016	Dec. 31, 2015	Jul. 29, 2011
4.50% Convertible Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	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%
8.375% Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	8.375%	8.375%