Employee Benefit Plans - Pension Plan Weighted-Average Asset Allocations (Details) - DB Pension Plans	Dec. 31, 2018	Dec. 31, 2017
Defined Contribution Plan Disclosure [Line Items]
Weighted-average asset allocations	100.00%	100.00%
Equity securities
Defined Contribution Plan Disclosure [Line Items]
Weighted-average asset allocations	65.00%	65.00%
Debt securities
Defined Contribution Plan Disclosure [Line Items]
Weighted-average asset allocations	34.00%	34.00%
Other
Defined Contribution Plan Disclosure [Line Items]
Weighted-average asset allocations	1.00%	1.00%