Equity - Stock Repurchase Activities (Details) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Feb. 28, 2017	Oct. 31, 2014	Feb. 28, 2014
Accelerated Share Repurchases [Line Items]
Shares Repurchased And Retired Related To Net Issuances		$ 1,200,000		$ 9,600,000
2014 Stock Repurchase Program [Member]
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount					$ 4,400,000,000		$ 2,100,000,000
Additional amount authorized under Stock Repurchase Plan					$ 500,000,000	$ 1,800,000,000.0
Stock repurchase program, remaining authorized repurchase amount	$ 469,700,000		$ 469,700,000
Stock repurchased (in shares)	4.0	5.5	8.5	8.6
Average price per share (in dollars per share)	$ 30.59	$ 23.08	$ 29.25	$ 23.37
Amount repurchased	$ 125,000,000	$ 125,500,000	$ 250,000,000	$ 200,500,000
Stock Repurchase Program 2014, Accelerated Share Repurchase [Member]
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount							$ 1,200,000,000