Equity, Stock Repurchase Activities (Details) $ / shares in Units, shares in Millions							3 Months Ended								12 Months Ended
	Oct. 22, 2015 $ / shares	Jul. 23, 2015 $ / shares	Apr. 23, 2015 $ / shares	Jan. 27, 2015 $ / shares	Oct. 23, 2014 $ / shares	Jul. 22, 2014 $ / shares	Dec. 31, 2015 USD ($) $ / shares	Sep. 30, 2015 $ / shares	Jun. 30, 2015 $ / shares	Mar. 31, 2015 $ / shares	Dec. 31, 2014 USD ($) $ / shares	Sep. 30, 2014 $ / shares	Jun. 30, 2014 $ / shares	Mar. 31, 2014 $ / shares	Dec. 31, 2015 USD ($) institution Dividend $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares	Jul. 31, 2015 USD ($)	Oct. 31, 2014 USD ($)	Feb. 28, 2014 USD ($)
Number of quarterly cash dividends declared | Dividend															4
Cash dividends declared per share of common stock (in dollars per share) | $ / shares	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0	$ 0	$ 0.40	$ 0.20	$ 0
Dividends paid															$ 156,300,000	$ 86,000,000	$ 0
Stock repurchase program, authorized amount																				$ 2,100,000,000
Repurchases under stock repurchase programs, shares repurchased | shares															45.4	46.8	28.9
Repurchases under stock repurchase programs, average price (in dollar per share) | $ / shares															$ 25.16	$ 22.42	$ 19.76
Repurchases under stock repurchase programs, amount repurchased															$ 1,142,500,000	$ 1,050,000,000	$ 570,600,000
Repurchases under accelerated share repurchase programs, shares repurchased | shares																49.3
Repurchases under accelerated share repurchase programs, average price per share (in dollar per share) | $ / shares																$ 24.35
Repurchases under stock repurchase programs, amount repurchased											$ 1,200,000,000					$ 1,200,000,000
Repurchases for tax withholding, shares repurchased | shares															0.4	0.6	0.4
Repurchases for tax withholding, average price per share (in dollar per share) | $ / shares															$ 26.70	$ 19.69	$ 20.23
Repurchases for tax withholding, amount repurchased															$ 11,100,000	$ 12,500,000	$ 7,200,000
Number of accelerated share repurchase programs | institution															2
Number of participating financial institutions in accelerated share repurchase programs | institution															2
Stock Repurchase Program 2014 [Member]
Stock repurchase program, authorized amount							$ 3,900,000,000								$ 3,900,000,000					$ 1,200,000,000
Additional amount authorized under Stock Repurchase Plan																		$ 500,000,000	$ 1,300,000,000.0
Stock repurchase program, remaining authorized repurchase amount							$ 532,500,000								$ 532,500,000