Income Taxes (Effective Income Tax Rate) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate			35.00%
Income tax benefit at the federal statutory rate			$ 223	$ 460
State income taxes, net of federal income tax effect			8	33
Cumulative effect of changes in corporate state income tax laws that were recognized within State income taxes, net of federal income tax effect			3	23
Temporary differences between carrying amounts of FCC licenses for financial statement purposes and their tax bases			(46)	0
Tax benefit from organizational restructuring			42	0
Change in federal and state valuation allowance			(522)	(647)
Other, net			6	5
Income tax benefit (expense)	$ (111)	$ (97)	$ (286)	$ (126)
Effective income tax rate			44.90%	9.60%