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)
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		3,352	[1]				3,352
Foreign currency translation adjustments, net of taxes		(91)	[2]					(91)
Net unrealized gains (losses) on debt securities, net of taxes		(139)	[1],[3]					(139)
Reclassification adjustment for convertible debt in mezzanine		3				3
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)				198,000
Exercise of stock options and vesting of restricted stock units and performance share units		$ 1		$ 0		1
Repurchase of common stock (in shares)		(2,095,017)			(2,095,000)
Repurchase of common stock		$ (4,181)			$ (4,181)
Stock-based compensation and other stock-based payments		220				220
Conversion of debt		(773)				(773)
Common stock issued in an acquisition (in shares)				52,000
Common stock issued in an acquisition		110		$ 0		110
Balance (in shares) at Sep. 30, 2018				62,939,000	(16,312,000)
Balance at Sep. 30, 2018		9,952		$ 0	$ (12,880)	5,344	17,721	(233)
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)
Increase (Decrease) in Stockholders' Equity
Net income		1,767	[1]				1,767
Foreign currency translation adjustments, net of taxes		(23)	[2]					(23)
Net unrealized gains (losses) on debt securities, net of taxes		(134)	[1],[3]					(134)
Reclassification adjustment for convertible debt in mezzanine		46				46
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)				12,000
Exercise of stock options and vesting of restricted stock units and performance share units		$ 0		$ 0		0
Repurchase of common stock (in shares)		(1,149,324)			(1,149,000)
Repurchase of common stock		$ (2,250)			$ (2,250)
Stock-based compensation and other stock-based payments		73				73
Balance (in shares) at Sep. 30, 2018				62,939,000	(16,312,000)
Balance at Sep. 30, 2018		9,952		$ 0	$ (12,880)	5,344	17,721	(233)
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		3,694	[1]				3,694
Foreign currency translation adjustments, net of taxes		(63)	[2]					(63)
Net unrealized gains (losses) on debt securities, net of taxes		114	[1],[3]					114
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)				213,000
Exercise of stock options and vesting of restricted stock units and performance share units		$ 1		$ 0		1
Repurchase of common stock (in shares)		(3,760,002)			(3,760,000)
Repurchase of common stock		$ (6,812)			$ (6,812)
Stock-based compensation and other stock-based payments		232				232
Balance (in shares) at Sep. 30, 2019				63,162,000	(21,077,000)
Balance at Sep. 30, 2019		5,951		$ 0	$ (21,523)	5,678	22,061	(265)
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)
Increase (Decrease) in Stockholders' Equity
Net income		1,950	[1]				1,950
Foreign currency translation adjustments, net of taxes		(35)	[2]					(35)
Net unrealized gains (losses) on debt securities, net of taxes	[1],[3]	0
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)				18,000
Exercise of stock options and vesting of restricted stock units and performance share units		$ 0		$ 0		0
Repurchase of common stock (in shares)		(698,774)			(699,000)
Repurchase of common stock		$ (1,350)			$ (1,350)
Stock-based compensation and other stock-based payments		79				79
Balance (in shares) at Sep. 30, 2019				63,162,000	(21,077,000)
Balance at Sep. 30, 2019		$ 5,951		$ 0	$ (21,523)	$ 5,678	$ 22,061	$ (265)

[1] The Company reclassified from accumulated other comprehensive income a net gain of $10 million ($11 million before tax) and a net loss of $1 million ($1 million before tax) for the nine months ended September 30, 2019 and 2018, respectively, from sales of investments in debt securities.
In addition, for both the three and nine months ended September 30, 2019, the Company reclassified from accumulated other comprehensive income a tax charge of $21 million related to the maturity in August 2019 of the Company's investment of $500 million in Trip.com Group (formerly known as Ctrip.com International Ltd.) convertible notes (see Note 5).
The reclassified net gain and loss before tax are included in "Foreign currency transactions and other" and the reclassified tax charges are included in "Income tax expense" 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.
Foreign currency translation adjustments, net of tax, includes foreign currency transaction gains of $85 million ($111 million before tax) and $112 million ($146 million before tax) for the three and nine months ended September 30, 2019, respectively, and foreign currency transaction gains of $17 million ($23 million before tax) and $111 million ($148 million before tax) for the three and nine months ended September 30, 2018, respectively, associated with the Company's Euro-denominated debt that is designated as a hedge against the impact of currency fluctuations on the net assets of a Euro functional currency subsidiary (see Note 9).
The Company recorded tax benefits of $8 million and $23 million for the three and nine months ended September 30, 2019, respectively, and tax benefits of $5 million and $16 million for the three and nine months ended September 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 enactment of the U.S. Tax Cuts and Jobs Act (the "Tax Act").

[3] Net unrealized gains on debt securities, net of tax, includes a tax benefit of $7 million and a tax charge of $30 million for the three and nine months ended September 30, 2019, respectively, in addition to the reclassified tax charges for both periods as disclosed in footnote (1) above. Net unrealized losses on debt securities, net of tax, for the nine months ended September 30, 2018, includes a tax benefit of $1 million.