Parent Company Financial Information (Condensed Statements of Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income
Interest-earning deposits									$ 109	$ 179	$ 355
Expense
Compensation and employee benefits									149,410	130,864	125,432
Other borrowings									553	593	734
Other expense									30,521	27,045	29,962
Income before income tax benefit and equity in undistributed (excess distributed) earnings of subsidiaries	$ 37,338	$ 37,295	$ 31,799	$ 35,188	$ 28,087	$ 31,188	$ 29,870	$ 28,640	141,620	117,785	87,010
Provision for income taxes	10,598	11,515	9,853	10,827	9,167	9,605	8,643	8,796	42,793	36,211	26,994
Net income	$ 26,740	$ 25,780	$ 21,946	$ 24,361	$ 18,920	$ 21,583	$ 21,227	$ 19,844	98,827	81,574	60,016
Parent Company [Member]
Income
Dividend from banking subsidiaries									67,000	16,200	183,000
Interest-earning deposits									5	25	68
Other income									92	10	7
Total Income									67,097	16,235	183,075
Expense
Compensation and employee benefits									618	530	658
Other borrowings									5	83	258
Other expense									1,368	1,433	4,162
Total Expenses									1,991	2,046	5,078
Income before income tax benefit and equity in undistributed (excess distributed) earnings of subsidiaries									65,106	14,189	177,997
Provision for income taxes									(663)	(704)	(1,552)
Income before equity in undistributed (excess distributed) earnings of subsidiaries									65,769	14,893	179,549
Equity in undistributed (excess distributed) earnings of subsidiaries									33,058	66,681	(119,533)
Net income									$ 98,827	$ 81,574	$ 60,016