Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Exercise of stock options	470,029	881,936	522,032
Purchase of treasury stock	111,252	104,836	54,295
Retirement of treasury stock			17,270,930
Common stock dividends/distributions	$ 3.02	$ 2.75	$ 2.50
Preferred stock dividend shares	$ 63.80	$ 63.80	$ 63.80
Additional Paid-in Capital [Member]
Exercise of stock options	470,029	881,936	522,032
Treasury Stock [Member]
Purchase of treasury stock	111,252	104,836	54,295
Retirement of treasury stock			17,270,930
Accumulated Deficit [Member]
Common stock dividends/distributions	$ 3.02	$ 2.75	$ 2.50
Preferred stock dividend shares	$ 63.80	$ 63.80	$ 63.80