Stock-Based Compensation Plans - Summary of Nonvested Performance Share Awards Activity (Details) - Performance Shares [Member] - $ / shares		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance	[1]	2,696,097
Granted		1,556,273
Change in performance		(118,398)
Vested		(704,141)
Forfeited		(52,167)
Undistributed vested awards	[2]	(820,505)
Ending Balance	[1]	2,557,159	2,696,097
Nonvested, Weighted Average Exercise Price (in usd per share)	[1]	$ 31.88	$ 30.62
Granted, Weighted Average Grant Date Fair Value (in usd per share)		35.88
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Change in Performance, Weighted Average Grant Date Fair Value		35.88
Vested, Weighted Average Exercise Price (in usd per share)		32.80
Forfeited, Weighted Average Exercise Price (in usd per share)		32.25
Undistributed Vested Awards, Weighted Average Grant Date Fair Value (in usd per share)	[2]	$ 33.95
Fully Vested Stock Based Compensation Issued To Retirement Eligible Employees		1,817,883	1,535,791

[1] Excludes 1,817,883 and 1,535,791 of performance share awards issued to retirement-eligible employees as of December 31, 2015 and 2014, respectively, as they are fully vested.

[2] Represents performance share awards that vested but were not distributed to retirement-eligible employees during 2015.