Label	Element	Value
Advisor Class | Mortgage-Backed Securities [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Total Investments	oef_PctOfTotalInv	95.70%
Advisor Class | U.S. Government and Agency Securities [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Total Investments	oef_PctOfTotalInv	2.40%
Advisor Class | Short-Term Investments [Member]
Holdings [Line Items]	oef_HoldingsLineItems
Percent of Total Investments	oef_PctOfTotalInv	1.90%