Parent Company Financial Information (Condensed Statements of Income) (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
Income
Deposits in banks									$ 216	$ 109	$ 179
Expense
Compensation and employee benefits									150,282	149,410	130,864
Other borrowings									545	553	593
Other expense									28,362	30,521	27,045
Income before income tax benefit and equity in undistributed (excess distributed) earnings of subsidiaries	$ 43,035	$ 39,608	$ 36,650	$ 30,488	$ 37,338	$ 37,295	$ 31,799	$ 35,188	149,781	141,620	117,785
Provision for income taxes	12,317	12,124	11,245	9,229	10,598	11,515	9,853	10,827	44,915	42,793	36,211
Net income	$ 30,718	$ 27,484	$ 25,405	$ 21,259	$ 26,740	$ 25,780	$ 21,946	$ 24,361	104,866	98,827	81,574
Parent Company [Member]
Income
Dividend from banking subsidiaries									83,500	67,000	16,200
Deposits in banks									4	5	25
Other income									8	92	10
Total Income									83,512	67,097	16,235
Expense
Compensation and employee benefits									543	618	530
Other borrowings									0	5	83
Other expense									1,608	1,368	1,433
Total Expenses									2,151	1,991	2,046
Income before income tax benefit and equity in undistributed (excess distributed) earnings of subsidiaries									81,361	65,106	14,189
Provision for income taxes									(748)	(663)	(704)
Income before equity in undistributed earnings of subsidiaries									82,109	65,769	14,893
Equity in undistributed earnings of subsidiaries									22,757	33,058	66,681
Net income									$ 104,866	$ 98,827	$ 81,574