Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Accounts receivable, allowances	$ 23,319	$ 21,015
Property and equipment, accumulated depreciation	$ 264,169	$ 245,718
Common stock, par value (in usd per share)	$ 2	$ 2
Common stock, authorized (shares)	200,000,000	200,000,000
Common stock, issued (shares)	63,737,000	62,843,000
Common stock, outstanding (shares)	63,737,000	62,843,000