CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($) $ / shares shares
Statement of Stockholders' Equity [Abstract]
Pension and other postretirement adjustments, tax	$ 962
Amortization of forward starting swaps, tax	$ 739
Issuance of common stock from performance share units and exercise of stock options (in shares) | shares	324,913
Issuance of common stock from exercise of stock options and deferred compensation plans, tax amount	$ 3,285
Purchase of common stock (in shares) | shares	147,490
Cash dividends declared, per common share outstanding (in dollars per share) | $ / shares	$ 0.86