Consolidated Statement of Shareholders' Equity Shareholders' Equity Parenthetical - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common Stock, Dividends, Per Share, Cash Paid	$ 0.44	$ 0.40	$ 0.36
Common Stock [Member]
Common Stock, Dividends, Per Share, Cash Paid	$ 0.44	$ 0.40	$ 0.36
Stock Issued During Period, Shares, New Issues	140,284	165,934	138,463
Stock Issued During Period, Shares, Share-based Compensation, Gross	0	599,673	738,025
Stock Issued During Period, Shares, Share-based Compensation, Forfeited	(99,927)	(343,929)	(408,638)
Shares of stock withheld for employee taxes	(91,100)	(63,235)	(168,490)
Stock Repurchased During Period, Shares	0	(785,542)	0