Parent Company Financial Information (Condensed Statements of Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income
Deposits in banks									$ 661	$ 1,312	$ 702
Expense
Compensation and employee benefits									209,722	212,867	200,199
Subordinated debentures									1,871	1,871	1,871
Other borrowings									196	669	504
Other expense									36,455	34,152	37,024
Income before income tax benefit and equity in undistributed (excess distributed) earnings of subsidiaries	$ 75,074	$ 54,683	$ 44,777	$ 17,858	$ 58,032	$ 63,105	$ 63,818	$ 56,656	192,392	241,611	211,836
Income Tax Expense (Benefit)	16,774	9,949	8,195	3,230	11,903	12,378	12,094	10,785	38,148	47,160	38,954
Net income	$ 58,300	$ 44,734	$ 36,582	$ 14,628	$ 46,129	$ 50,727	$ 51,724	$ 45,871	154,244	194,451	172,882
Parent Company
Income
Dividend from banking subsidiaries									89,000	168,000	85,250
Deposits in banks									13	100	12
Other income									37	68	56
Total Income									89,050	168,168	85,318
Expense
Compensation and employee benefits									758	791	978
Subordinated debentures									1,871	1,871	1,871
Other borrowings									12	0	4
Other expense									1,943	2,111	2,058
Total Expenses									4,584	4,773	4,911
Income before income tax benefit and equity in undistributed (excess distributed) earnings of subsidiaries									84,466	163,395	80,407
Income Tax Expense (Benefit)									(952)	(967)	(1,017)
Income before equity in undistributed earnings of subsidiaries									85,418	164,362	81,424
Equity in undistributed earnings of subsidiaries									68,826	30,089	91,458
Net income									$ 154,244	$ 194,451	$ 172,882