Stock-Based Compensation Plans (Weighted-Average Assumptions used to Determine Fair Value of Stock Acquisition Rights Granted) (Detail)		12 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Share-based Payment Arrangement [Abstract]
Risk-free interest rate		0.70%	1.37%	1.14%
Expected lives		5 years 8 months 23 days	5 years 11 months 23 days	6 years 6 months 18 days
Expected volatility	[1]	29.30%	32.52%	38.49%
Expected dividends		0.32%	0.35%	0.40%

[1] Expected volatility was based on the historical volatilities of Sony Corporation’s common stock over the expected life of the stock acquisition rights.