Incentive Plans (Changes in Stock Options Outstanding) (Details) - $ / shares		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of Shares
Exercised	[1]		(15,575)	(119,994)
Outstanding at end of year		5,757,435
Exercisable at end of year		3,830,535
Stock Options [Member]
Number of Shares
Outstanding at beginning of year		5,443,288	5,602,250	6,006,585
Granted at FMV		862,000	991,000	772,900
Exercised			(32,349)	(862,407)
Forfeited		(547,853)	(1,117,613)	(314,828)
Outstanding at end of year		5,757,435	5,443,288	5,602,250
Exercisable at end of year		3,830,535	3,542,352	3,030,105	2,435,322
Average Exercise Price
Outstanding at beginning of year		$ 52.93	$ 57.95	$ 56.80
Granted at FMV		17.57	49.67	55.82
Exercised			40.80	49.27
Forfeited		44.23	31.99	54.53
Outstanding at end of year		48.46	52.93	57.95
Exercisable at end of year		$ 53.80	$ 52.26	$ 53.10	$ 51.79

[1] Shares issued upon exercise of stock options and award of restricted stock are less than the amount reflected in Note J due to withholdings for statutory income taxes owed upon issuance of shares.