Parent Company Financial Statements (Condensed Statements of Income and Comprehensive 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
EXPENSES
Salaries and Employee Benefits									$ 51,306	$ 46,642	$ 43,961
Professional Fees									5,362	2,817	3,672
Interest Expense									19,139	11,121	8,461
INCOME BEFORE INCOME TAXES AND EQUITY IN UNDISTRIBUTED INCOME OF SUBSIDIARIES									56,057	52,210	49,130
Income Tax Benefit									(9,528)	(11,534)	(13,946)
NET INCOME	$ 10,980	$ 12,639	$ 11,097	$ 11,813	$ 11,621	$ 9,660	$ 9,839	$ 9,556	46,529	40,676	35,184
Other Comprehensive Income:
COMPREHENSIVE INCOME									42,051	44,929	24,968
Parent Company
INCOME
Interest Income									38	34	20
Other Income (Loss)									(13)	25	(27)
Total Income									8,225	26,034	15,993
EXPENSES
Salaries and Employee Benefits									576	533	1,006
Professional Fees									2,079	602	1,096
Occupancy and Equipment Expense									7	7	13
Interest Expense									1,279	877	742
Other Expenses									813	794	750
Total Expenses									4,754	2,813	3,607
INCOME BEFORE INCOME TAXES AND EQUITY IN UNDISTRIBUTED INCOME OF SUBSIDIARIES									3,471	23,221	12,386
Income Tax Benefit									1,042	1,415	1,284
INCOME BEFORE EQUITY IN UNDISTRIBUTED INCOME OF SUBSIDIARIES									4,513	24,636	13,670
Equity in Undistributed Income of Subsidiaries									42,016	16,040	21,514
NET INCOME									46,529	40,676	35,184
Other Comprehensive Income:
Changes in Unrealized Gain (Loss) on Securities, Available-for-Sale									(4,424)	4,391	(10,202)
Changes in Unrecognized Loss in Postretirement Benefit Obligation, Net									(54)	(138)	(14)
COMPREHENSIVE INCOME									42,051	44,929	24,968
Parent Company | Bank
INCOME
Dividends from Subsidiaries									7,000	25,000	15,000
Parent Company | Non-bank
INCOME
Dividends from Subsidiaries									$ 1,200	$ 975	$ 1,000