Retirement Plans - Schedule of Plan Assets Fair Value Hierarchy (Details) - United Kingdom Subsidiary - UK Plan - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 264,194	$ 295,968	$ 257,236
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16,097	25,502
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	125,573	166,521
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	122,524	103,945	$ 0
Equity and equity like investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35,425	41,684
Equity and equity like investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Equity and equity like investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35,425	41,684
Equity and equity like investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	135,780	173,575
Corporate debt securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Corporate debt securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	37,703	69,630
Corporate debt securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	98,077	103,945
Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52,445	55,207
Government bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Government bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52,445	55,207
Government bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16,097	25,502
Cash | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16,097	25,502
Cash | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Cash | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	$ 0
Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24,447
Real estate | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Real estate | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Real estate | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 24,447