Incentive Plans - Schedule of Activity Relating to RSUs and DSUs (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units, Beginning Balance	21,481,131	20,751,829	22,108,635
Units, Granted	5,174,810	8,594,744	7,002,736
Units, Forfeited	(268,900)	(581,411)	(305,155)
Units, Vested	(9,768,849)	(7,284,031)	(8,054,387)
Units, Ending Balance	16,618,192	21,481,131	20,751,829
Weighted Average Grant Date Fair Value, Beginning Balance	$ 33.92	$ 36.84	$ 35.67
Weighted Average Grant Date Fair Value, Granted	$ 37.21	$ 27.68	$ 43.21
Weighted Average Grant Date Fair Value, Forfeited	$ 34.47	$ 35.59	$ 37.83
Weighted Average Grant Date Fair Value, Vested	$ 34.65	$ 34.71	$ 39.13
Weighted Average Grant Date Fair Value, Ending Balance	$ 34.51	$ 33.92	$ 36.84
DSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units, Beginning Balance	204,496	140,660	121,737
Units, Granted	46,938	63,836	35,043
Units, Forfeited
Units, Vested			(16,120)
Units, Ending Balance	251,434	204,496	140,660
Weighted Average Grant Date Fair Value, Beginning Balance	$ 31.47	$ 34.83	$ 34.46
Weighted Average Grant Date Fair Value, Granted	$ 34.42	$ 24.06	$ 36.09
Weighted Average Grant Date Fair Value, Forfeited
Weighted Average Grant Date Fair Value, Vested			$ 34.76
Weighted Average Grant Date Fair Value, Ending Balance	$ 32.02	$ 31.47	$ 34.83