Average Annual Total Returns{- Fidelity Flex Inflation-Protected Bond Index Fund} - 12.31 Fidelity Flex Inflation-Protected Bond Index Fund PRO-09 - Fidelity Flex Inflation-Protected Bond Index Fund	Fidelity Flex Inflation-Protected Bond Index Fund Return Before Taxes Past 1 year	Fidelity Flex Inflation-Protected Bond Index Fund Return Before Taxes Since Inception		Fidelity Flex Inflation-Protected Bond Index Fund After Taxes on Distributions Past 1 year	Fidelity Flex Inflation-Protected Bond Index Fund After Taxes on Distributions Since Inception		Fidelity Flex Inflation-Protected Bond Index Fund After Taxes on Distributions and Sales Past 1 year	Fidelity Flex Inflation-Protected Bond Index Fund After Taxes on Distributions and Sales Since Inception		LB124 Past 1 year	LB124 Since Inception
Total	5.92%	5.58%	[1]	3.87%	4.44%	[1]	3.50%	3.83%	[1]	5.96%	5.62%	[1]

[1] ^(a)From March 9, 2017