Income Taxes - Components of Net Deferred Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Deferred tax assets	$ 280,117	$ 203,876
Less: valuation allowance	(8,084)	(12,306)
Net deferred tax assets	272,033	191,570
Deferred tax liabilities
Deferred tax liabilities	(307,678)	(263,813)
Net deferred tax liabilities	(35,645)	(72,243)
United States
Deferred tax assets
Net operating loss carry forwards	129,695	95,577
Disallowed interest deduction carryforwards	92,030	51,423
Deferred pension plan amounts	10,447	11,887
Accrued expenses not currently deductible	8,434	9,688
Other	2,356	1,936
Deferred tax liabilities
Excess of net book basis over remaining tax basis	(299,136)	(254,669)
Other	(2,420)	(6,482)
Non-US
Deferred tax assets
Net operating loss carry forwards	22,426	26,441
Disallowed interest deduction carryforwards	13,942	6,254
Deferred pension plan amounts	787	670
Deferred tax liabilities
Excess of net book basis over remaining tax basis	(4,780)	(1,066)
Other	$ (1,342)	$ (1,596)