UNAUDITED CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total		Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity
Cumulative effect of adoption of accounting standards updates	$ 189					$ 430	$ (241)
Balance (in shares) at Dec. 31, 2017			62,689,000	(14,217,000)
Balance at Dec. 31, 2017	11,261		$ 0	$ (8,699)	$ 5,783	13,939	238
Increase (Decrease) in Stockholders' Equity
Net income	1,585	[1]				1,585
Foreign currency translation adjustments, net of taxes	(68)	[2]					(68)
Net unrealized gains (losses) on marketable securities, net of taxes	(5)						(5)
Reclassification adjustment for convertible debt in mezzanine	(43)				(43)
Exercise of stock options and vesting of restricted stock units and/or performance share units (in shares)			186,000
Exercise of stock options and vesting of restricted stock units and/or performance share units	$ 1		$ 0		1
Repurchase of common stock (in shares)	(945,693)			(946,000)
Repurchase of common stock	$ (1,931)			$ (1,931)
Stock-based compensation and other stock-based payments	147				147
Conversion of debt	(773)				(773)
Common stock issued in an acquisition (in shares)			52,000
Common stock issued in an acquisition	110				110
Balance (in shares) at Jun. 30, 2018			62,927,000	(15,163,000)
Balance at Jun. 30, 2018	10,473		$ 0	$ (10,630)	5,225	15,954	(76)
Balance (in shares) at Mar. 31, 2018			62,838,000	(14,590,000)
Balance at Mar. 31, 2018	10,636		$ 0	$ (9,431)	5,033	14,976	58
Increase (Decrease) in Stockholders' Equity
Net income	978	[1]				978
Foreign currency translation adjustments, net of taxes	(129)	[2]					(129)
Net unrealized gains (losses) on marketable securities, net of taxes	(5)						(5)
Reclassification adjustment for convertible debt in mezzanine	5				5
Exercise of stock options and vesting of restricted stock units and/or performance share units (in shares)			37,000
Exercise of stock options and vesting of restricted stock units and/or performance share units	$ 1		$ 0		1
Repurchase of common stock (in shares)	(572,574)			(573,000)
Repurchase of common stock	$ (1,199)			$ (1,199)
Stock-based compensation and other stock-based payments	76				76
Common stock issued in an acquisition (in shares)			52,000
Common stock issued in an acquisition	110				110
Balance (in shares) at Jun. 30, 2018			62,927,000	(15,163,000)
Balance at Jun. 30, 2018	10,473		$ 0	$ (10,630)	5,225	15,954	(76)
Balance (in shares) at Dec. 31, 2018			62,949,000	(17,317,000)
Balance at Dec. 31, 2018	8,785		$ 0	$ (14,711)	5,445	18,367	(316)
Increase (Decrease) in Stockholders' Equity
Net income	1,744	[1]				1,744
Foreign currency translation adjustments, net of taxes	(28)	[2]					(28)
Net unrealized gains (losses) on marketable securities, net of taxes	114						114
Exercise of stock options and vesting of restricted stock units and/or performance share units (in shares)			195,000
Exercise of stock options and vesting of restricted stock units and/or performance share units	$ 1		$ 0		1
Repurchase of common stock (in shares)	(3,061,228)			(3,061,000)
Repurchase of common stock	$ (5,462)			$ (5,462)
Stock-based compensation and other stock-based payments	153				153
Balance (in shares) at Jun. 30, 2019			63,144,000	(20,378,000)
Balance at Jun. 30, 2019	5,307		$ 0	$ (20,173)	5,599	20,111	(230)
Balance (in shares) at Mar. 31, 2019			63,122,000	(18,936,000)
Balance at Mar. 31, 2019	6,915		$ 0	$ (17,567)	5,519	19,132	(169)
Increase (Decrease) in Stockholders' Equity
Net income	979	[1]				979
Foreign currency translation adjustments, net of taxes	(16)	[2]					(16)
Net unrealized gains (losses) on marketable securities, net of taxes	(45)						(45)
Exercise of stock options and vesting of restricted stock units and/or performance share units (in shares)			22,000
Exercise of stock options and vesting of restricted stock units and/or performance share units	$ 1		$ 0		1
Repurchase of common stock (in shares)	(1,442,440)			(1,442,000)
Repurchase of common stock	$ (2,606)			$ (2,606)
Stock-based compensation and other stock-based payments	79				79
Balance (in shares) at Jun. 30, 2019			63,144,000	(20,378,000)
Balance at Jun. 30, 2019	$ 5,307		$ 0	$ (20,173)	$ 5,599	$ 20,111	$ (230)

[1] The Company reclassified from accumulated other comprehensive income net gains of $10 million ($9 million, net of tax) and $11 million ($10 million, net of tax) for the three and six months ended June 30, 2019, respectively, and a net loss of $1 million ($1 million, net of tax) for the six months ended June 30, 2018 from sales of investments in debt securities. The reclassified net gains (losses) are included in "Foreign currency transactions and other" in the Unaudited Consolidated Statements of Operations.

[2] Foreign currency translation adjustments result from currency fluctuations on the translation of the Company's non-U.S. Dollar functional currency subsidiaries' net assets, net of the impact of net investment hedges.
The Company recorded tax benefits of $4 million and $15 million for the three and six months ended June 30, 2019, respectively, and tax benefits of $21 million and $11 million for the three and six months ended June 30, 2018, respectively, related to foreign currency translation adjustments to its one-time deemed repatriation tax liability recorded at December 31, 2017 and foreign earnings for periods after December 31, 2017 that are subject to U.S. federal and state income tax, resulting from the introduction of the U.S. Tax Cuts and Jobs Act (the "Tax Act").
Foreign currency translation adjustments also include a tax benefit of $11 million and a tax charge of $8 million for the three and six months ended June 30, 2019, respectively, and tax charges of $57 million and $31 million for the three and six months ended June 30, 2018, respectively, associated with the Company's Euro-denominated debt that is designated as a net investment hedge against the impact of currency fluctuations on the net assets of a Euro functional currency subsidiary (see Note 9).