Recently Issued Accounting Standards (Details) - USD ($) $ in Millions		6 Months Ended
Jan. 01, 2018	Jun. 30, 2018
Accounting Policies [Abstract]
Reclassification from accumulated other comprehensive income to retained earnings	$ 0.2	$ 0.2

Amount of increase (decrease) in accumulated other comprehensive income (AOCI) for reclassification to retained earnings of tax effect from remeasurement of deferred tax pursuant to Tax Cuts and Jobs Act of 2017.

No definition available.

Name:	fbm_TaxCutsAndJobsActOf2017ReclassificationFromAociToRetainedEarningsTaxEffect
Namespace Prefix:	fbm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration