Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Allowance for doubtful accounts	$ 76,061	$ 53,412
Contract asset, allowance for doubtful accounts	3,043
Accumulated depreciation on property, plant and equipment	1,068,613	1,013,207
Other assets, allowance for credit loss	$ 97,897	$ 101,439
Shareholders’ equity:
Common shares, par value (in dollars per share)	$ 1.25	$ 1.25
Common shares, shares authorized (in shares)	305,000	305,000
Common shares, shares issued (in shares)	176,793	176,793
Treasury shares, shares (in shares)	46,775	46,262