BASIS OF PRESENTATION Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Mar. 31, 2018	Sep. 30, 2018
Reclassification of certain tax affects from tax law changes, 2018-02		$ 253
Reclassification of accumulated unrealized gains on available-for-sale securities, ASU 2016-01		$ 9
Adjustments for New Accounting Principle, Early Adoption
Reclassification of certain tax affects from tax law changes, 2018-02	$ 253
Reclassification of accumulated unrealized gains on available-for-sale securities, ASU 2016-01	$ 9

Reclassification from Accumulated Other Comprehensive Income to retained earnings, adoption of accounting standard

No definition available.

Name:	wy_ReclassificationfromAccumulatedOtherComprehensiveIncometoretainedearningsadoptionofaccountingstandard
Namespace Prefix:	wy_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration