Summary Of Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total interest income	$ 133,109		$ 132,533		$ 135,422		$ 128,888		$ 129,801		$ 127,575		$ 120,549		$ 119,144		$ 529,952		$ 497,069		$ 374,746
Total interest expense	8,292		10,083		10,306		7,866		5,913		4,779		3,875		3,663		36,547		18,230		6,757
Net Interest Income	124,817		122,450		125,116		121,022		123,888		122,796		116,674		115,481		493,405		478,839		367,989
Provision for loan and lease losses	1,614		299		218		1,362		1,789		3,153		3,975		5,852		3,493		14,769		8,631
Noninterest income	21,807		28,030		25,648		21,696		20,402		21,019		23,692		23,143		97,181		88,256		109,642
Noninterest expense	86,978		87,076		86,728		84,700		87,019		82,841		84,643		85,987		345,482		340,490		291,017
Income before income taxes	58,032		63,105		63,818		56,656		55,482		57,821		51,748		46,785		241,611		211,836		177,983
Provision for income taxes	11,903		12,378		12,094		10,785		10,734		11,406		9,999		6,815		47,160		38,954		65,155
Net income	$ 46,129		$ 50,727		$ 51,724		$ 45,871		$ 44,748		$ 46,415		$ 41,749		$ 39,970		$ 194,451		$ 172,882		$ 112,828
Per Common Share
Earnings (basic)	$ 0.64	[1]	$ 0.70	[1]	$ 0.71	[1]	$ 0.63	[1]	$ 0.61	[1]	$ 0.63	[1]	$ 0.57	[1]	$ 0.55	[1]	$ 2.68	[1]	$ 2.36	[1]	$ 1.86
Earnings (diluted)	$ 0.64	[1]	$ 0.70	[1]	$ 0.71	[1]	$ 0.63	[1]	$ 0.61	[1]	$ 0.63	[1]	$ 0.57	[1]	$ 0.55	[1]	$ 2.68	[1]	$ 2.36	[1]	$ 1.86

[1] Due to averaging of shares, quarterly EPS may not add up to the totals reported for the full year.