Capital Transactions - Repurchase Programs (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2013	Jan. 31, 2019	Feb. 02, 2017
Equity, Class of Treasury Stock [Line Items]
Repurchase of shares of common stock (in shares)		429,000,000
Share Repurchase Program 2017
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, dollar amount authorized				$ 1,000,000,000
Cost of common stock repurchased under the stock repurchase program	$ 0
Repurchase of shares of common stock (in shares)	0
Subsequent Events | Share Repurchase Program 2019
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, dollar amount authorized			$ 1,500,000,000