Employer Sponsored Benefit Plans - Target Allocation and the Actual Allocation of Plan Assets (Details)	Dec. 31, 2018	Dec. 31, 2017
Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation of Plan Assets (as a percent)	16.00%	26.00%
International equities
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation of Plan Assets (as a percent)	11.00%	26.00%
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation of Plan Assets (as a percent)	44.00%	40.00%
U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation of Plan Assets (as a percent)	3.00%	0.00%
Corporate and foreign bonds
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation of Plan Assets (as a percent)	2.00%	0.00%
Inflation hedge mutual funds
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation of Plan Assets (as a percent)	3.00%	0.00%
Hedge fund of funds
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation of Plan Assets (as a percent)	5.00%	7.00%
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation of Plan Assets (as a percent)	16.00%	1.00%
Minimum | Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	11.00%
Minimum | International equities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	5.00%
Minimum | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	30.00%
Minimum | U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	2.00%
Minimum | Corporate and foreign bonds
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	2.00%
Minimum | Inflation hedge mutual funds
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	2.00%
Minimum | Hedge fund of funds
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	2.00%
Minimum | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	0.00%
Maximum | Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	32.00%
Maximum | International equities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	24.00%
Maximum | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	69.00%
Maximum | U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	13.00%
Maximum | Corporate and foreign bonds
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	13.00%
Maximum | Inflation hedge mutual funds
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	13.00%
Maximum | Hedge fund of funds
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	9.00%
Maximum | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Target Allocation (as a percent)	32.00%