Stockholders' Equity (Details 2) - USD ($)	3 Months Ended							12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Aug. 06, 2014	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase of treasury stock value									$ 527,000,000	$ 1,924,000,000
Stock repurchase accrued but unpaid	$ 0								$ 0
Number of treasury shares retired								2,400,000	10,700,000
Treasury Stock, Retired, Cost Method, Amount								$ 0	$ 0
Treasury stock, shares	2,411,839							27,602	2,411,839
Change in common shares issued and outstanding
Beginning balance				241,673,050			279,240,970	233,081,556	241,673,050	279,240,970
Exercise of stock options								17,600	274,705	942,560
Issuance of restricted stock								44,941	40,673	20,875
Forfeitures of restricted stock								(10,000)	0	(65,680)
Purchase of treasury shares								(19,928)	(8,906,872)	(38,465,675)
Ending balance	233,081,556				241,673,050			233,114,169	233,081,556	241,673,050	279,240,970
The 2012 Share Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum amount up to which company common stock is authorized to be repurchased													$ 3,000,000,000
Purchase of treasury shares						(15,400,000)	(16,000,000)			(31,400,000)	(36,700,000)
Purchase of treasury stock value						$ 757,000,000	$ 794,000,000			$ 1,551,000,000	$ 1,449,000,000
The 2014 Share Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum amount up to which company common stock is authorized to be repurchased												$ 1,000,000,000
Purchase of treasury shares	0	(300,000)	(4,500,000)	(4,100,000)	(7,000,000)				(8,900,000)	(7,000,000)
Purchase of treasury stock value	$ 0	$ 22,000,000	$ 268,000,000	$ 237,000,000	$ 373,000,000				$ 527,000,000	$ 373,000,000
Paid-In Capital
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury Stock, Retired, Cost Method, Amount								$ 14,000,000	62,000,000	220,000,000
Retained Earnings
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury Stock, Retired, Cost Method, Amount								136,000,000	535,000,000	1,685,000,000
Treasury Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase of treasury stock value									527,000,000	1,924,000,000
Treasury Stock, Retired, Cost Method, Amount								$ (150,000,000)	$ (597,000,000)	$ (1,906,000,000)