Summary of Significant Accounting Policies - Other Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Advertising expense	$ 281	$ 135	$ 117
Deferred Revenue & Deposits [Abstract]
Deferred revenue, rate payable to developer upon utilization of virtual currency	70.00%
Deferred revenue	$ 28	38
Deposits	28	28
Total deferred revenue and deposits	$ 56	$ 66
Maximum
Operating Leased Assets [Line Items]
Lease expiration year	2032