Summary Of Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Total interest income	$ 86,734		$ 86,758		$ 83,303		$ 81,174		$ 82,769		$ 82,665		$ 82,040		$ 81,417		$ 337,969		$ 328,891		$ 308,042
Total interest expense	997		1,186		1,163		1,004		950		971		1,030		1,053		4,350		4,004		3,994
Net Interest Income	85,737		85,572		82,140		80,170		81,819		81,694		81,010		80,364		333,619		324,887		304,048
Provision for loan and lease losses	18		1,866		3,640		5,254		2,349		2,831		2,202		1,209		10,778		8,591		6,727
Noninterest income	22,330		23,166		21,940		20,646		24,745		22,499		21,462		22,767		88,082		91,473		59,750
Noninterest expense	65,014		67,264		63,790		65,074		66,877		64,067		68,471		66,734		261,142		266,149		239,286
Income before income taxes	43,035		39,608		36,650		30,488		37,338		37,295		31,799		35,188		149,781		141,620		117,785
Provision for income taxes	12,317		12,124		11,245		9,229		10,598		11,515		9,853		10,827		44,915		42,793		36,211
Net income	$ 30,718		$ 27,484		$ 25,405		$ 21,259		$ 26,740		$ 25,780		$ 21,946		$ 24,361		$ 104,866		$ 98,827		$ 81,574
Per Common Share
Earnings (basic)	$ 0.53	[1]	$ 0.47	[1]	$ 0.44	[1]	$ 0.37	[1]	$ 0.46	[1]	$ 0.45	[1]	$ 0.38	[1]	$ 0.42	[1]	$ 1.81	[1]	$ 1.71	[1]	$ 1.53
Earnings (diluted)	$ 0.53	[1]	$ 0.47	[1]	$ 0.44	[1]	$ 0.37	[1]	$ 0.46	[1]	$ 0.45	[1]	$ 0.38	[1]	$ 0.42	[1]	$ 1.81	[1]	$ 1.71	[1]	$ 1.52

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