Employee Benefit Plans - Pension Plan Participants (Details) - Pension Plan		12 Months Ended
	Dec. 31, 2008	Dec. 31, 2019
Employee benefit plans
Required service period to participate in the plan		1 year
Vesting percentage for employees already enrolled with at least five years of service as of effective date of plan change	100.00%
Minimum service period for employees already enrolled to be 100% vested as of effective date of plan change	5 years
Vesting period if minimum service period for employees already enrolled was not met as of effective date of plan change	5 years