CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) $ / shares shares
Statement of Stockholders' Equity [Abstract]
Pension and other postretirement adjustments, tax	$ 1,417
Amortization of forward starting swaps, tax	$ 1,105
Issuance of common stock from performance share units and exercise of stock options (in shares) | shares	563,193
Issuance of common stock from exercise of stock options and deferred compensation plans, tax amount	$ 4,144
Purchase of common stock (in shares) | shares	356,590
Cash dividends declared, per common share outstanding (in dollars per share) | $ / shares	$ 1.29