Unsecured Borrowings - Unsecured Long-Term Borrowings after Hedging (Parenthetical) (Detail)	Sep. 30, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
Effective weighted average interest rates for unsecured long-term borrowings, after hedging - total	2.06%	2.87%
Effective weighted average interest rates for unsecured long-term borrowings, after hedging fixed rate obligations	3.61%	3.77%
Effective weighted average interest rates for unsecured long-term borrowings, after hedging - floating rate obligations	1.70%	2.48%