Retirement Plans - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Pension costs		$ 3,200,000	$ 7,800,000
Employer contributions	$ 9,300,000	$ 7,700,000
Estimated net actuarial gain to be amortized	0
Estimated prior service cost to be amortized (less than)	100,000
Company contributions	1,200,000
Impact of .5% increase on post retirement benefit obligation	(2,100,000)
Impact of .5% increase on post retirement cost	(100,000)
Impact of .5% decrease on post retirement benefit obligation	2,400,000
Impact of .5% decrease on post retirement cost	200,000
Impact of .5% increase on assumed long-term rate of return on plan assets	(100,000)
Impact of .5% decrease on assumed long-term rate of return on plan assets	$ 100,000
Nonqualified Plan
Defined Contribution Plan Disclosure [Line Items]
Employee matching contribution, percent of employee deferral	6.00%
Employer matching contribution, percent of match	3.00%
Scenario One | Qualified Plan
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent of match	100.00%
Employer matching contribution, percent of employees' gross pay	3.00%
Scenario Two | Qualified Plan
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent of match	50.00%
Employer matching contribution, percent of employees' gross pay	2.00%
WestRock cash balance
Defined Contribution Plan Disclosure [Line Items]
Employer transition contribution, percentage of employee's gross pay	4.00%
Final average pay pension
Defined Contribution Plan Disclosure [Line Items]
Employer transition contribution, percentage of employee's gross pay	10.00%