Income Taxes - Principal Reasons for the Difference Between the Effective Tax Rate and UBT Statutory Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Amount [Abstract]
UBT statutory rate	$ 32,937	$ 33,012	$ 30,956
Corporate subsidiaries' federal, state, and local	4,000	1,522	2,558
Foreign subsidiaries taxed at different rates	26,719	30,689	25,406
2017 Tax Act	0	1,155	25,846
FIN 48 reserve (release)	2,765	(5,177)	(3,318)
UBT business allocation percentage rate change	(79)	2,657	0
Deferred tax and payable write-offs	314	2,932	(9,542)
Foreign outside basis difference	155	2,273	0
Amended 2017 return	(3,853)	0	0
Effect of ASC 740 adjustments, miscellaneous taxes, and other	2,305	(2,521)	1,903
Income not taxable resulting from use of UBT business apportionment factors and effect of compensation charge	(23,509)	(20,726)	(20,699)
Income tax expense	$ 41,754	$ 45,816	$ 53,110
Effective Income Tax Rate Reconciliation, Percent [Abstract]
UBT statutory rate, percent	4.00%	4.00%	4.00%
Corporate subsidiaries' federal, state, and local, percent	0.50%	0.20%	0.30%
Foreign subsidiaries taxed at different rates, percent	3.30%	3.70%	3.30%
2017 Tax Act, percent	0	0.001	0.033
FIN 48 release, percent	0.30%	(0.60%)	(0.40%)
UBT Bap Rate Change, percent	0.00%	0.30%	0.00%
Deferred tax and payable write-offs, percent	0.00%	0.40%	(1.20%)
Foreign outside basis difference, percent	0.00%	0.30%	0.00%
Amended 2017 return, percent	(0.50%)	0.00%	0.00%
Effect of ASC 740 adjustments, miscellaneous taxes, and other, percent	0.30%	(0.30%)	0.20%
Income not taxable resulting from use of UBT business apportionment factors and effect of compensation charge, percent	(2.80%)	(2.50%)	(2.60%)
Effective tax rate, percent	5.10%	5.60%	6.90%