Parent Company Only Financial Information (Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income	$ 37,851	$ 34,612	$ 45,169	$ 31,497	$ 32,141	$ 33,710	$ 27,879	$ 23,268	$ 149,129	$ 116,998	$ 75,272
Adjustments to reconcile net income to net cash provided by operating activities:
Securities gains, net									(7,659)	(1,085)	(6,973)
Gain on extinguishment of debt									(375)	0	(1,280)
Excess tax benefits from stock based compensation									266	674	1,246
Other, net									(34,786)	(8,760)	(14,148)
NET CASH PROVIDED BY OPERATING ACTIVITIES									161,174	242,750	155,930
Cash flows from investing activities:
Repayment of advances from subsidiaries									6,000	0	0
Proceeds from sales of available for sale securities									1,628,467	727,895	1,456,750
Net assets acquired									76,071	212,197	71,089
NET CASH PROVIDED (USED) BY INVESTING ACTIVITIES									(573,970)	(124,220)	27,298
Cash flows from financing activities:
Proceeds on short-term revolving credit line									0	25,000	20,000
Proceeds from other borrowings									50	30,131	0
Repayments on short-term revolving credit line									0	(25,000)	(20,000)
Repayments of other borrowings									(20,693)	(59,157)	(9,645)
Payment for the redemption of debt									(2,125)	0	(13,800)
Cash dividends paid									(24,607)	(19,357)	(14,557)
Purchase of treasury stock									0	(97)	(625)
Proceeds from issuance of common stock									661	489	963
NET CASH PROVIDED (USED) BY FINANCING ACTIVITIES									517,900	(40,903)	(145,949)
Net increase in cash and cash equivalents									105,104	77,627	37,279
Cash and cash equivalents at beginning of year				273,630				196,003	273,630	196,003	158,724
CASH AND CASH EQUIVALENTS AT END OF PERIOD	378,734				273,630				378,734	273,630	196,003
Supplemental disclosure:
Conversion of convertible debt to common stock									0	0	558
Conversion/redemption of Series D preferred stock to common stock									0	938	419
Stock consideration granted for acquisitions									92,258	238,075	175,196
Parent
Cash flows from operating activities:
Net income									149,129	116,998	75,272
Adjustments to reconcile net income to net cash provided by operating activities:
Undistributed earnings of subsidiaries									(34,307)	(52,570)	(16,212)
Securities gains, net									0	0	(3,021)
Gain on extinguishment of debt									(375)	0	(1,200)
Increase (decrease) in accrued expenses and other liabilities									3,274	5,336	(4,160)
Increase in other assets									(12,248)	(1,559)	(567)
Excess tax benefits from stock based compensation									270	674	1,246
Other, net									4,103	5,401	4,714
NET CASH PROVIDED BY OPERATING ACTIVITIES									109,846	74,280	56,072
Cash flows from investing activities:
Capital contributions to subsidiaries									(46,583)	(30,696)	0
Proceeds from sales of available for sale securities									0	0	2,868
Proceeds from the sale, maturity of and principal paydowns on other investments									0	0	211
Net assets acquired									(594)	(13,504)	(62,813)
NET CASH PROVIDED (USED) BY INVESTING ACTIVITIES									(41,177)	(44,200)	(59,734)
Cash flows from financing activities:
Proceeds on short-term revolving credit line									0	25,000	20,000
Proceeds from other borrowings									0	30,000	0
Repayments on short-term revolving credit line									0	(25,000)	(20,000)
Repayments of other borrowings									(20,023)	(25,759)	(9,016)
Payment for the redemption of debt									(2,500)	0	(13,800)
Cash dividends paid									(24,607)	(19,357)	(14,557)
Purchase of treasury stock									0	(97)	(625)
Proceeds from issuance of common stock									661	489	963
NET CASH PROVIDED (USED) BY FINANCING ACTIVITIES									(46,469)	(14,724)	(37,035)
Net increase in cash and cash equivalents									22,200	15,356	(40,697)
Cash and cash equivalents at beginning of year				$ 39,666				$ 24,310	39,666	24,310	65,007
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 61,866				$ 39,666				61,866	39,666	24,310
Supplemental disclosure:
Conversion of convertible debt to common stock									0	0	558
Conversion/redemption of Series D preferred stock to common stock									0	938	419
Stock consideration granted for acquisitions									$ 92,258	$ 238,075	$ 175,196