Business Combinations - Business Acquisition, Pro Forma Information (Details) - USD ($) $ / shares in Units, $ 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
Net Interest Income	$ 60,816	$ 60,159	$ 62,449	$ 54,522	$ 36,241	$ 35,683	$ 35,241	$ 33,919	$ 237,946		$ 141,084		$ 124,717
Provision for loan losses	(6,158)	3,658	1,868	43,786	1,084	1,327	282	212	43,154	[1]	2,905	[1]	1,176	[1]
Noninterest Income	61,731	50,477	51,329	218	28,375	27,627	28,792	27,971	163,755		112,765		106,997
Noninterest Expense	41,313	43,563	37,984	42,310	24,720	23,265	24,320	24,779	165,170		97,084		89,330
Income before income taxes	39,088	31,914	36,360	(28,093)	15,470	16,204	14,958	14,005	79,269		60,637		56,875
Income Tax Expense	$ 8,240	$ 6,259	$ 7,303	$ (5,610)	$ 2,952	$ 3,033	$ 2,759	$ 2,523	16,192		11,267		$ 10,626
Pro Forma [Member]
Net Interest Income									215,922		212,498
Provision for loan losses									18,295		3,195
Noninterest Income									83,966		71,202
Noninterest Expense									154,544		166,429
Income before income taxes									127,049		114,076
Income Tax Expense									26,216		21,478
Net Income									$ 100,833		$ 92,598
Diluted Earnings Per Share									$ 2.66		$ 2.44

[1] Beginning January 1, 2020, calculation is based on current expected loss methodology.  Prior to January 1, 2020, calculation was based on incurred loss methodology.