Summary of Significant Accounting Policies - Financial Statement Effects of Topic 606 (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue	$ 3,807	$ 3,898	$ 3,665	$ 3,580	$ 3,312	$ 3,398	$ 3,053	$ 2,734	$ 14,950	$ 12,497	$ 10,776
Advertising and marketing									907	771	698
Income before income taxes									7,204	6,522	5,646
Income tax expense									1,345	2,607	1,587
Net Income	899	$ 1,899	$ 1,569	$ 1,492	227	$ 1,430	$ 1,177	$ 1,081	5,859	3,915	$ 4,059
Accounts receivable	2,276				1,969				2,276	1,969		$ 2,013
Prepaid expenses and other current assets	1,432				1,040				1,432	1,040		1,204
Deferred income taxes	570				250				570	250		367
Other assets	3,303				2,298				3,303	2,298		2,636
Accounts payable	537				933				537	933		438
Accrued expenses	4,747				3,931				4,747	3,931		4,322
Other current liabilities	949				792				949	792		748
Other liabilities	1,877				1,438				1,877	1,438		2,066
Retained earnings	27,283				$ 22,364				27,283	$ 22,364		22,547
Balances excluding revenue standard
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									14,471
Advertising and marketing									743
Income before income taxes									6,889
Income tax expense									1,278
Net Income									5,611
Accounts receivable	2,214								2,214
Prepaid expenses and other current assets	1,176								1,176
Deferred income taxes	666								666
Other assets	2,388								2,388
Accounts payable	959								959
Accrued expenses	4,375								4,375
Other current liabilities	1,085								1,085
Other liabilities	1,145								1,145
Retained earnings	26,692								26,692
Impact of revenue standard | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue									479
Advertising and marketing									164
Income before income taxes									315
Income tax expense									67
Net Income									248
Accounts receivable	62								62			44
Prepaid expenses and other current assets	256								256			181
Deferred income taxes	(96)								(96)			(69)
Other assets	915								915			690
Accounts payable	(422)								(422)			(495)
Accrued expenses	372								372			391
Other current liabilities	(136)								(136)			(44)
Other liabilities	732								732			628
Retained earnings	$ 591								$ 591			$ 366