Shareholder Report, Average Annual Return (Details)	12 Months Ended	60 Months Ended	120 Months Ended
Shareholder Report, Average Annual Return (Details)	Jul. 31, 2026	Jul. 31, 2026	Jul. 31, 2026
C000019282_1_BBIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	2.71%
C000019282_1_BBIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		(0.40%)
C000019282_1_BBIndexMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			1.35%
C000019282_NoLoadClassMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.28%
C000019282_NoLoadClassMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.31%
C000019282_NoLoadClassMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			1.18%
C000019282_0_AdditionalIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.09%
C000019282_0_AdditionalIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.35%
C000019282_0_AdditionalIndexMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			1.20%