Shareholder Report, Average Annual Return (Details)	12 Months Ended	60 Months Ended	120 Months Ended
Shareholder Report, Average Annual Return (Details)	Jan. 31, 2026	Jan. 31, 2026	Jan. 31, 2026
C000019544_1_BBIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.70%
C000019544_1_BBIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.86%
C000019544_1_BBIndexMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			2.32%
C000205010_1_BBIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.70%
C000205010_1_BBIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.86%
C000205010_1_BBIndexMember_LOCMember
Average Annual Return [Line Items]
Average Annual Return, Percent	2.62%
C000019548_1_BBIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.70%
C000019548_1_BBIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.86%
C000019548_1_BBIndexMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			2.32%
C000019549_1_BBIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.70%
C000019549_1_BBIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.86%
C000019549_1_BBIndexMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			2.32%
C000019547_1_BBIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.70%
C000019547_1_BBIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.86%
C000019547_1_BBIndexMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			2.32%
C000019545_1_BBIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.70%
C000019545_1_BBIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.86%
C000019545_1_BBIndexMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			2.32%
C000019544_NoLoadClassMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.56%
C000019544_NoLoadClassMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.88%
C000019544_NoLoadClassMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			2.14%
C000019544_0_AdditionalIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.23%
C000019544_0_AdditionalIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.72%
C000019544_0_AdditionalIndexMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			2.26%
C000205010_NoLoadClassMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.67%
C000205010_NoLoadClassMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.91%
C000205010_NoLoadClassMember_2025-02-01_2026-01-31Member
Average Annual Return [Line Items]
Average Annual Return, Percent	2.58%
C000205010_0_AdditionalIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.23%
C000205010_0_AdditionalIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.72%
C000205010_0_AdditionalIndexMember_LOCMember
Average Annual Return [Line Items]
Average Annual Return, Percent	2.56%
C000019548_ClassMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	0.19%
C000019548_ClassMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		(0.21%)
C000019548_ClassMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			1.45%
C000019548_NoLoadClassMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.36%
C000019548_NoLoadClassMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.61%
C000019548_NoLoadClassMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			1.86%
C000019548_0_AdditionalIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.23%
C000019548_0_AdditionalIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.72%
C000019548_0_AdditionalIndexMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			2.26%
C000019549_NoLoadClassMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.56%
C000019549_NoLoadClassMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.79%
C000019549_NoLoadClassMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			2.06%
C000019549_0_AdditionalIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.23%
C000019549_0_AdditionalIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.72%
C000019549_0_AdditionalIndexMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			2.26%
C000019547_ClassMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	2.59%
C000019547_ClassMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		(0.15%)
C000019547_ClassMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			1.23%
C000019547_NoLoadClassMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	3.59%
C000019547_NoLoadClassMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		(0.15%)
C000019547_NoLoadClassMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			1.23%
C000019547_0_AdditionalIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.23%
C000019547_0_AdditionalIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.72%
C000019547_0_AdditionalIndexMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			2.26%
C000019545_ClassMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	0.15%
C000019545_ClassMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		(0.26%)
C000019545_ClassMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			1.40%
C000019545_NoLoadClassMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.32%
C000019545_NoLoadClassMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.56%
C000019545_NoLoadClassMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			1.82%
C000019545_0_AdditionalIndexMember_1YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent	4.23%
C000019545_0_AdditionalIndexMember_5YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent		0.72%
C000019545_0_AdditionalIndexMember_10YRMember
Average Annual Return [Line Items]
Average Annual Return, Percent			2.26%