Third Avenue Value Portfolio Market Risk [Member] Style Risk [Member] Smalland Mid Cap Risk [Member] Commodities Risk [Member] Foreign Securitiesand Emerging Markets Risk [Member] Currency Risk [Member] Currency Hedging Risk [Member] Japanese Securities Risk [Member] Canadian Securities Risk [Member] Liquidity Risk [Member] Debt Securities Risk [Member] High Yield Risk [Member] Insolvencyand Bankruptcy Risk [Member] Focused Investing Risk [Member] Third Avenue Value Portfolio MSCI World Index (reflects no deductions for fees, expenses or taxes) Third Avenue Value Portfolio [Default Label]