Income Taxes - Earnings Before Income Taxes and Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings before income taxes:
United States	$ 743,687	$ 697,501	$ 672,221
Foreign	163,749	125,936	153,093
Total	907,436	823,437	825,314
Income tax expense:
Partnership UBT	3,356	9,196	5,251
Corporate subsidiaries:
Federal	1,495	(943)	(4,030)
State and local	904	975	2,888
Foreign	44,086	32,290	36,529
Current tax expense	49,841	41,518	40,638
Deferred tax	(4,188)	236	5,178
Income tax expense	$ 45,653	$ 41,754	$ 45,816