Recently Issued Accounting Pronouncements - Modified Retrospective Method - Adjusted Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Accounts receivable, net	$ 1,035	$ 921	$ 918
Software development	264	347	367
Other current assets	539	441	476
Deferred income taxes, net	403	427	459
Other assets	482	444	440
Liabilities and Shareholders’ Equity
Deferred revenues	1,493	1,735	1,929
Accrued expenses and other liabilities	896		1,411
Other liabilities	1,147	1,155	1,132
Shareholders’ equity	11,357	9,553	9,462	$ 9,119	$ 8,068
Calculated under Revenue Guidance in Effect before Topic 606
Assets
Accounts receivable, net	1,037		918
Software development	266		367
Other current assets	559		476
Deferred income taxes, net	453		459
Other assets	493		440
Liabilities and Shareholders’ Equity
Deferred revenues	1,674		1,929
Accrued expenses and other liabilities	914
Other liabilities	1,102		1,132
Shareholders’ equity	11,288		$ 9,462
Difference between Revenue Guidance in Effect before and after Topic 606 | Adjustments For ASU 2014-09
Assets
Accounts receivable, net	(2)	3
Software development	(2)	(20)
Other current assets	(20)	(35)
Deferred income taxes, net	(50)	(32)
Other assets	(11)	4
Liabilities and Shareholders’ Equity
Deferred revenues	(181)	(194)
Accrued expenses and other liabilities	(18)
Other liabilities	45	23
Shareholders’ equity	$ 69	$ 91