Incentive Plans (Changes in Stock Options Outstanding) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Number of Shares
Exercised		[1]	0	(15,575)	[1]
Outstanding at end of year	4,901,269
Exercisable at end of year	3,197,269
Stock Options [Member]
Number of Shares
Outstanding at beginning of year	5,757,435		5,443,288	5,602,250
Granted at FMV	603,000		862,000	991,000
Exercised				(32,349)
Forfeited	(1,459,166)		(547,853)	(1,117,613)
Outstanding at end of year	4,901,269		5,757,435	5,443,288
Exercisable at end of year	3,197,269		3,830,535	3,542,352		3,030,105
Average Exercise Price
Outstanding at beginning of year	$ 48.46		$ 52.93	$ 57.95
Granted at FMV	28.51		17.57	49.67
Exercised				40.80
Forfeited	49.34		44.23	31.99
Exercisable at end of year	54.22		53.80	52.26		$ 53.10
Outstanding at end of year	$ 45.74		$ 48.46	$ 52.93

[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.