Parent Company Financial Statements (Statement of Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income:
Total income									$ 194,404	$ 184,340	$ 175,607
Expenses:
Interest on junior subordinated debentures									869	613	491
Legal and professional fees									2,427	2,294	2,579
Change in fair value of contingent consideration									(187)	(643)	(898)
Income before income taxes	$ 21,559	$ 22,252	$ 22,416	$ 20,465	$ 21,145	$ 19,288	$ 19,704	$ 17,503	86,692	77,640	68,854
Income tax benefit (expense)	(4,523)	(4,741)	(4,742)	(4,254)	(13,163)	(6,326)	(6,505)	(5,721)	(18,260)	(31,715)	(22,373)
Net income	$ 17,036	$ 17,511	$ 17,674	$ 16,211	$ 7,982	$ 12,962	$ 13,199	$ 11,782	68,432	45,925	46,481
Parent Company [Member]
Income:
Other income									0	0	1
Total income									32,418	27,918	24,557
Expenses:
Interest on junior subordinated debentures									869	613	491
Legal and professional fees									187	169	98
Change in fair value of contingent consideration									(187)	(643)	(898)
Other									324	298	282
Total expenses									1,193	437	(27)
Income before income taxes									31,225	27,481	24,584
Income tax benefit (expense)									284	340	(15)
Income before equity in undistributed earnings of subsidiaries									31,509	27,821	24,569
Net income									68,432	45,925	46,481
Bank [Member]
Income:
Dividends from subsidiaries									32,394	27,900	24,442
Expenses:
Equity in undistributed earnings (losses) of subsidiaries									36,876	18,193	22,008
Non-bank [Member]
Income:
Dividends from subsidiaries									24	18	114
Expenses:
Equity in undistributed earnings (losses) of subsidiaries									$ 47	$ (89)	$ (96)