Consolidated Statements Of Comprehensive Income - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 171,040,000	$ 189,589,000	$ 139,445,000
Other comprehensive income (loss):
Change in unrealized net holding gains (losses) on securities	59,851,000	(16,201,000)	(5,796,000)
Reclassification adjustments for gains realized in income	(282,000)	0	(301,000)
Tax effect	(17,715,000)	4,996,000	2,570,000
Other comprehensive income (loss), net of tax	41,854,000	(11,205,000)	(3,527,000)
Total comprehensive income	$ 212,894,000	$ 178,384,000	$ 135,918,000