Description Of Business And Basis of Presentation New revenue standard adoption - Income Statement at Period End (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended														12 Months Ended
	Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019		Mar. 31, 2018	Mar. 31, 2017
Condensed Income Statements, Captions [Line Items]
Net revenue	$ 1,238	[1]	$ 1,289	[1]	$ 1,286	[1]	$ 1,137	[1]	$ 1,582		$ 1,160		$ 959	$ 1,449	$ 4,950	[1]	$ 5,150	$ 4,845
Cost of Revenue															1,322		1,277	1,298
Gross profit	962		876		868		922		1,349		659		570	1,295	3,628		3,873	3,547
Operating Expenses															2,632		2,439	2,323
Operating Income (Loss)	196		242		258		300		753		(21)		(41)	743	996		1,434	1,224
Other Nonoperating Income (Expense)															83		15	(14)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest															1,079		1,449	1,210
Income Tax Expense (Benefit)															60		406	243
Net income (loss)	$ 209		$ 262		$ 255		$ 293		$ 607	[2]	$ (186)	[2]	$ (22)	$ 644	$ 1,019		$ 1,043	$ 967
Earnings Per Share, Basic	$ 0.70		$ 0.87		$ 0.84		$ 0.96		$ 1.98		$ (0.60)		$ (0.07)	$ 2.08	$ 3.36		$ 3.39	$ 3.19
Earnings Per Share, Diluted	$ 0.69		$ 0.86		$ 0.83		$ 0.95		$ 1.95		$ (0.60)		$ (0.07)	$ 2.06	$ 3.33		$ 3.34	$ 3.08
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Condensed Income Statements, Captions [Line Items]
Net revenue															$ 107
Cost of Revenue															188
Gross profit															(81)
Operating Expenses															0
Operating Income (Loss)															(81)
Other Nonoperating Income (Expense)															0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest															(81)
Income Tax Expense (Benefit)															(14)
Net income (loss)															$ (67)
Earnings Per Share, Basic															$ (0.22)
Earnings Per Share, Diluted															$ (0.22)
Difference between Revenue Guidance in Effect before and after Topic 606, Percentage [Member]
Condensed Income Statements, Captions [Line Items]
Revenues, percent															2.00%
Cost of revenue, percent															17.00%
Gross profit, percent															(2.00%)
Operating expenses, percent															0.00%
Operating income (loss), percent															(8.00%)
Other nonoperating income (expense), percent															0.00%
Income before provision for income taxes, percent															(7.00%)
Income tax expense (benefit), percent															(19.00%)
Net income (loss), percent															(6.00%)
Earnings per share, basic, percent															(6.00%)
Earnings per share, diluted, percent															(6.00%)
Product [Member]
Condensed Income Statements, Captions [Line Items]
Net revenue															$ 1,593		$ 2,586	$ 2,640
Cost of Revenue															517		822	893
Product [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Condensed Income Statements, Captions [Line Items]
Net revenue															(611)
Cost of Revenue															$ (120)
Product [Member] | Difference between Revenue Guidance in Effect before and after Topic 606, Percentage [Member]
Condensed Income Statements, Captions [Line Items]
Revenues, percent															(28.00%)
Cost of revenue, percent															(19.00%)
Service and other [Member]
Condensed Income Statements, Captions [Line Items]
Net revenue															$ 3,357		2,564	2,205
Cost of Revenue															805		$ 455	$ 405
Service and other [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Condensed Income Statements, Captions [Line Items]
Net revenue															718
Cost of Revenue															$ 308
Service and other [Member] | Difference between Revenue Guidance in Effect before and after Topic 606, Percentage [Member]
Condensed Income Statements, Captions [Line Items]
Revenues, percent															27.00%
Cost of revenue, percent															62.00%
Accounting Standards Update 2014-09 [Member]
Condensed Income Statements, Captions [Line Items]
Net revenue															$ 4,950
Cost of Revenue															1,322
Gross profit															3,628
Operating Expenses															2,632
Operating Income (Loss)															996
Other Nonoperating Income (Expense)															83
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest															1,079
Income Tax Expense (Benefit)															60
Net income (loss)															$ 1,019
Earnings Per Share, Basic															$ 3.36
Earnings Per Share, Diluted															$ 3.33
Accounting Standards Update 2014-09 [Member] | Product [Member]
Condensed Income Statements, Captions [Line Items]
Net revenue															$ 1,593
Cost of Revenue															517
Accounting Standards Update 2014-09 [Member] | Service and other [Member]
Condensed Income Statements, Captions [Line Items]
Net revenue															3,357
Cost of Revenue															805
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Condensed Income Statements, Captions [Line Items]
Net revenue															4,843
Cost of Revenue															1,134
Gross profit															3,709
Operating Expenses															2,632
Operating Income (Loss)															1,077
Other Nonoperating Income (Expense)															83
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest															1,160
Income Tax Expense (Benefit)															74
Net income (loss)															$ 1,086
Earnings Per Share, Basic															$ 3.58
Earnings Per Share, Diluted															$ 3.55
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Product [Member]
Condensed Income Statements, Captions [Line Items]
Net revenue															$ 2,204
Cost of Revenue															637
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Service and other [Member]
Condensed Income Statements, Captions [Line Items]
Net revenue															2,639
Cost of Revenue															$ 497

[1] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjI5NjBiOTQwMmRkNjQxNGFiYmUwMjhiM2Y5YmZiYzllfFRleHRTZWxlY3Rpb246MjBGRDJFMzhGM0YxNUE2QTA4QzA3QjU2M0ZERDRDOUUM}

[2] During the quarters ended December 31, 2017 and March 31, 2018, we recognized tax expense of $176 million and $59 million, respectively, due to the application of the U.S. Tax Act, enacted on December 22, 2017.