Pension and Other Postretirement Benefit Plans - Summary of Fair Value of LPP Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]
Total plan assets at fair value	$ 338,264	$ 312,455
Money market mutual fund
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]
Total plan assets at fair value	4,506	2,311
Real Estate
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]
Total plan assets at fair value	9,948	20,836
Common Collective Trusts | Fixed income securities
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]
Total plan assets at fair value		181,156
Common Collective Trusts | Global equity securities
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]
Total plan assets at fair value	323,810	108,152
Fair Value, Inputs, Level 1
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]
Total plan assets at fair value	4,506	2,311
Fair Value, Inputs, Level 1 | Money market mutual fund
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]
Total plan assets at fair value	4,506	2,311
Fair Value, Inputs, Level 2
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]
Total plan assets at fair value	323,810	289,308
Fair Value, Inputs, Level 2 | Common Collective Trusts | Fixed income securities
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]
Total plan assets at fair value		181,156
Fair Value, Inputs, Level 2 | Common Collective Trusts | Global equity securities
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]
Total plan assets at fair value	323,810	108,152
Fair Value, Inputs, Level 3
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]
Total plan assets at fair value	9,948	20,836
Fair Value, Inputs, Level 3 | Real Estate
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]
Total plan assets at fair value	$ 9,948	$ 20,836	$ 19,455