Income Taxes Income Tax Expense Components (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Current federal tax expense (benefit)									$ 13,198	$ 10,699	$ (2,469)
Current foreign tax expense (benefit)									10,132	9,147	16,640
Current state and local tax expense (benefit)									1,548	725	600
Current income tax expense (benefit)									24,878	20,571	14,771
Deferred federal income tax expense (benefit)									(1,340)	(2,948)	1,844
Deferred foreign income tax expense (benefit)									1,909	626	(5,845)
Deferred state and local income tax expense (benefit)									0	0	85
Deferred income tax expense (benefit)									569	(2,322)	(3,916)
Income tax expense	$ 5,750	$ 9,404	$ 5,020	$ 5,273	$ 8,016	$ 3,595	$ 3,709	$ 2,929	$ 25,447	$ 18,249	$ 10,855