Retirement Plans - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) plan	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	$ 25,226	$ 23,417	$ 24,036
Defined benefit plan, voluntary contribution	$ 1,112	24,862
Corridor amount	10.00%
Net unrecognized actuarial losses expected to be recognized in 2018	$ 10,400
Net unrecognized actuarial losses expected to be recognized in 2018, net of tax	7,800
Net periodic benefit cost (income), non-service cost	$ 3,559	(2,590)	$ (179)
Unfunded Plan | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Number of frozen, nonqualified unfunded defined benefit pension plans | plan	2
U.S.
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, planned contributions for each of next 5 years	$ 9,000
Defined benefit plan, voluntary contribution		$ 10,000
Increase (decrease) in projected benefit obligation	$ (3,580)
Discount rate used to compute periodic benefit cost	2.72%
Expected long-term rates of return on plans' assets in next fiscal year	5.50%
U.K Plan
Defined Benefit Plan Disclosure [Line Items]
Number of defined benefit plans | plan	3
Discount rate used to compute periodic benefit cost	1.71%
Expected long-term rates of return on plans' assets in next fiscal year	2.54%