CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Stockholders' Equity [Abstract]
Tax benefit (expense) on change in retirement obligations, tax	$ 3,842	$ (6,852)	$ 13,085
Tax benefit from change on derivatives designated as cash flow hedges, tax	$ 2,499	$ 2,713	$ 2,629
Issuance of common stock from issuance of unvested shares, exercise of stock options and deferred compensation plans, shares	685,501	571,751	1,471,568
Issuance of common stock from issuance of unvested shares, exercise of stock options and deferred compensation plans, tax	$ 3,794	$ 3,425	$ 4,514
Repurchase of common stock, shares	2,811,002	2,970,461	2,916,280
Cash dividends declared, per common share outstanding	$ 1.28	$ 1.12	$ 0.89