Employee Benefit Plans - Fair Value of Pension Plan Assets (Details) - Pension Plans - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 1,978,708	$ 1,725,543	$ 1,941,330
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,860,490	1,603,707
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	118,218	121,836	$ 114,593
U.S. common collective trusts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	384,739	315,741
U.S. common collective trusts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. common collective trusts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	384,739	315,741
U.S. common collective trusts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign common collective trusts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	379,717	352,040
Foreign common collective trusts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign common collective trusts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	379,717	352,040
Foreign common collective trusts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	84,519	79,155
Corporate bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	84,519	79,155
Corporate bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Common collective trusts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,011,515	856,771
Common collective trusts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Common collective trusts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,011,515	856,771
Common collective trusts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Private equity and hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	118,218	121,836
Private equity and hedge funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Private equity and hedge funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Private equity and hedge funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 118,218	$ 121,836