CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Stockholders' Equity [Abstract]
Tax benefit (expense) on change in retirement obligations, tax	$ (2,107)	$ (3,842)	$ 6,852
Tax benefit from change on derivatives designated as cash flow hedges, tax	$ 2,490	$ 2,499	$ 2,713
Issuance of common stock from issuance of unvested shares, exercise of stock options and deferred compensation plans (in shares)	594,919	685,501	571,751
Issuance of common stock from issuance of unvested shares, exercise of stock options and deferred compensation plans, tax	$ 5,305	$ 3,794	$ 3,425
Repurchase of common stock (in shares)	738,593	2,811,002	2,970,461
Cash dividends declared, per common share outstanding (in dollars per share)	$ 1.36	$ 1.28	$ 1.12