Capital Structure - Summary of Changes in Shares Repurchased (Details) - USD ($) $ / shares in Units, $ in Millions	2 Months Ended	12 Months Ended	14 Months Ended
	Feb. 28, 2019	Dec. 31, 2018	Feb. 28, 2019
Capital Allocation Plan [Line Items]
Total number of shares purchased (in shares)		35,234,664
Capital Allocation Plan, Open Market Repurchases
Capital Allocation Plan [Line Items]
Total number of shares purchased (in shares)		11,097,631,000,000
Amounts paid for shares purchased (in millions)		$ 396
Capital Allocation Plan, Accelerated Repurchase Agreement May 2018
Capital Allocation Plan [Line Items]
Total number of shares purchased (in shares)		10,829,903,000,000
Amounts paid for shares purchased (in millions)		$ 354
Capital Allocation Plan, Accelerated Repurchase Program September 2018
Capital Allocation Plan [Line Items]
Total number of shares purchased (in shares)		13,307,130,000,000
Amounts paid for shares purchased (in millions)		$ 500
Capital Allocation Plan
Capital Allocation Plan [Line Items]
Total number of shares purchased (in shares)		35,234,664,000,000
Amounts paid for shares purchased (in millions)		$ 1,250
Subsequent Event | Capital Allocation Plan, Open Market Repurchases
Capital Allocation Plan [Line Items]
Total number of shares purchased (in shares)	6,153,415,000,000
Amounts paid for shares purchased (in millions)	$ 250
Subsequent Event | Capital Allocation Plan
Capital Allocation Plan [Line Items]
Total number of shares purchased (in shares)			41,388,079,000,000
Average price paid per share (in shares)			$ 36.24
Amounts paid for shares purchased (in millions)			$ 1,500