Condensed Financial Information (parent company only) - Statement of Cash Flows (Details) - USD ($) $ 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
Cash Flow From Operating Activities:
Net income	$ 22,293	$ 21,059	$ 20,006	$ 17,693	$ 14,177	$ 17,067	$ 17,968	$ 16,172	$ 81,051	$ 65,384	$ 60,162
Adjustments to Reconcile Net Income to Net Cash:
Share-based compensation									2,600	2,270	2,177
Gain on sale of insurance subsidiary										(8,265)
Gain on cancellation of subordinated debentures										(1,250)
Net Change in:
Net cash provided by operating activities									106,860	56,660	75,840
Cash Flows from Investing Activities:
Purchase of securities available for sale									(281,470)	(200,154)	(110,936)
Net cash paid in acquisition										(7,936)	(10,084)
Other									(4,490)	9	5,889
Net cash used in investing activities									(451,845)	(340,391)	(125,991)
Cash Flows from Financing Activities:
Repayment of borrowings									(982,449)	(370,813)	(789,563)
Stock issued under employee benefit plans									462	460	478
Stock issued under dividend reinvestment and stock purchase plan									835	661	523
Stock options exercised									2,495	1,461	504
Stock redeemed									(1,980)	(1,640)	(1,067)
Net cash provided by financing activities									370,742	267,285	59,333
Cash and Cash Equivalents, beginning of the year				102,170				118,616	102,170	118,616	109,434
Cash and Cash Equivalents, end of year	127,927				102,170				127,927	102,170	118,616
Parent
Cash Flow From Operating Activities:
Net income									81,051	65,384	60,162
Adjustments to Reconcile Net Income to Net Cash:
Share-based compensation									1,166	843	887
Distributions in excess of (equity in undistributed) income of subsidiaries									(53,551)	(31,087)	(14,579)
Gain on sale of insurance subsidiary										(8,265)
Gain on cancellation of subordinated debentures										(1,250)
Net Change in:
Other assets									833	(441)	2,425
Other liabilities									849	(1,486)	1,466
Investment in subsidiaries - operating activities									(1,938)	197	(4,517)
Net cash provided by operating activities									28,410	23,895	45,844
Cash Flows from Investing Activities:
Purchase of securities available for sale									(19,804)
Net cash paid in acquisition										(14,500)	(12,832)
Proceeds from business divestitures										16,000
Other										575
Net cash used in investing activities									(19,804)	2,075	(12,832)
Cash Flows from Financing Activities:
Cash dividends									(22,203)	(15,654)	(10,694)
Repayment of borrowings										(3,750)
Proceeds from issuance of long-term debt
Preferred stock redemption under small business lending fund
Stock issued under employee benefit plans									462	460	478
Stock issued under dividend reinvestment and stock purchase plan									835	661	523
Stock options exercised									2,602	1,531	564
Stock redeemed									(1,980)	(1,640)	(1,067)
Net cash provided by financing activities									(20,284)	(18,392)	(10,196)
Cash and Cash Equivalents, beginning of the year				$ 43,622				$ 36,044	43,622	36,044	13,228
Cash and Cash Equivalents, end of year	$ 31,944				$ 43,622				$ 31,944	$ 43,622	$ 36,044