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, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Amount [Abstract]
UBT statutory rate	$ 33,012	$ 30,956	$ 28,927
Corporate subsidiaries' federal, state, and local	1,522	2,558	5,820
Foreign subsidiaries taxed at different rates	30,689	25,406	23,646
2017 Tax Act	1,155	25,846	0
FIN 48 release	(5,177)	(3,318)	0
UBT BAP Rate Change	2,657	0	0
Deferred tax and payable write-offs	2,932	(9,542)	(14,883)
Foreign outside basis difference	2,273	0	0
Effect of ASC 740 adjustments, miscellaneous taxes, and other	(2,521)	1,903	2,254
Income not taxable resulting from use of UBT business apportionment factors and effect of compensation charge	(20,726)	(20,699)	(17,445)
Income tax expense	$ 45,816	$ 53,110	$ 28,319
Effective Income Tax Rate Reconciliation, Percent [Abstract]
UBT statutory rate, percent	4.00%	4.00%	4.00%
Corporate subsidiaries' federal, state, and local, percent	0.20%	0.30%	0.80%
Foreign subsidiaries taxed at different rates, percent	3.70%	3.30%	3.30%
2017 Tax Act, percent	0.10%	3.30%	0.00%
FIN 48 release, percent	(0.60%)	(0.40%)	(0.00%)
UBT Bap Rate Change, percent	0.30%	0.00%	0.00%
Deferred tax and payable write-offs, percent	0.40%	(1.20%)	(2.10%)
Foreign outside basis difference, percent	0.30%	0.00%	0.00%
Effect of ASC 740 adjustments, miscellaneous taxes, and other, percent	(0.30%)	0.20%	0.30%
Income not taxable resulting from use of UBT business apportionment factors and effect of compensation charge, percent	(2.50%)	(2.60%)	(2.40%)
Effective tax rate, percent	5.60%	6.90%	3.90%