Parent Company Income Statement (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
Condensed Financial Statements, Captions [Line Items]
Derivative Asset		$ 26,113				$ 17,318				$ 26,113	$ 17,318
Expenses
Interest expense		7,618	$ 6,641	$ 5,999	$ 5,278	5,044	$ 4,705	$ 4,378	$ 4,207	25,536	18,334	$ 18,793
Income tax benefit		8,258	9,969	9,249	6,828	14,915	12,681	10,731	9,014	34,304	47,341	35,427
Net Income		29,934	$ 33,015	$ 31,118	$ 27,555	22,064	$ 23,852	$ 20,563	$ 20,725	121,622	87,204	76,648
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividend Income, Operating	[1]									71,255	47,006	44,598
Derivative Asset	[2]	$ 1,711				$ 1,535				1,711	1,535
Income
Interest income(2)	[3]										50	98
Total income										71,255	47,056	44,696
Expenses
Interest expense										4,234	3,995	5,901
Total expenses										4,234	3,995	5,901
Income before income taxes and equity in undistributed income of subsidiaries										67,021	43,061	38,795
Income tax benefit										(1,151)	(1,523)	(1,791)
Income of parent company										68,172	44,584	40,586
Equity in undistributed income of subsidiaries										53,450	42,620	36,062
Net Income										$ 121,622	$ 87,204	$ 76,648

[1] eliminates in consolidation.

[2] Entire balance eliminates in consolidation.

[3] Entire balance eliminated in consolidation.