CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Tax expense on change in retirement obligations, tax	$ 3,076	$ 239	$ 2,107
Tax from change on derivatives designated as cash flow hedges, tax	$ 1,469	$ 2,445	$ 2,490
Issuance of common stock from issuance of unvested shares, exercise of stock options and deferred compensation plans (in shares)	583,385	557,591	594,919
Issuance of common stock from issuance of unvested shares, exercise of stock options and deferred compensation plans, tax	$ 4,267	$ 6,027	$ 5,305
Repurchase of common stock (in shares)	1,273,961	266,000	738,593
Cash dividends declared, per common share outstanding (in dollars per share)	$ 1.72	$ 1.48	$ 1.36