Employee Benefit Plans - Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Plan assets, at fair value	$ 745,858	$ 844,588
Investments at Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets, at fair value	617,858	671,718
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets, at fair value	128,000	172,870
Mutual funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets, at fair value	128,000	172,870
Mutual funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets, at fair value	0	0
Mutual funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets, at fair value	$ 0	$ 0