Parent Company Financial Statements (Statements of Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 43,465	$ 40,824	$ 36,153
Adjustments to reconcile net income to net cash provided by operating activities:
Decrease in other assets	4,458	8,250	(1,717)
Net cash provided by operating activities	51,566	2,648	79,816
Cash flows from investing activities:
Repayment of investment in capital trust	0	0	310
Cash used in business combination, net of cash acquired	(1,671)	0	0
Net cash used in investing activities	(165,885)	(357,372)	(184,062)
Cash flows from financing activities:
Proceeds from stock option exercises and issuance of other equity instruments	1,563	1,189	3,681
Tax benefit from stock option exercises and other equity instruments	694	578	570
Redemption of junior subordinated debentures	0	0	(10,310)
Cash dividends paid	(22,770)	(19,722)	(16,628)
Net cash provided by financing activities	131,600	349,757	96,913
Net increase (decrease) in cash and cash equivalents	17,281	(4,967)	(7,333)
Cash and cash equivalents at beginning of year	80,350	85,317	92,650
Cash and cash equivalents at end of year	97,631	80,350	85,317
Parent Company [Member]
Cash flows from operating activities:
Net income	43,465	40,824	36,153
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of subsidiary	(21,104)	(21,554)	(12,899)
Increase in dividend receivable	19	(495)	(408)
Decrease in other assets	(67)	183	397
Decrease in accrued expenses and other liabilities	2,466	(516)	(621)
Other, net	(3,363)	(245)	(214)
Net cash provided by operating activities	21,416	18,197	22,408
Cash flows from investing activities:
Repayment of investment in capital trust	0	0	310
Cash used in business combination, net of cash acquired	(1,671)	0	0
Net cash used in investing activities	(1,671)	0	310
Cash flows from financing activities:
Issuance of treasury stock, including net deferred compensation plan activity	0	0	30
Proceeds from stock option exercises and issuance of other equity instruments	1,563	1,189	3,651
Tax benefit from stock option exercises and other equity instruments	694	578	570
Redemption of junior subordinated debentures	0	0	(10,310)
Cash dividends paid	(22,770)	(19,722)	(16,628)
Net cash provided by financing activities	(20,513)	(17,955)	(22,687)
Net increase (decrease) in cash and cash equivalents	(768)	242	31
Cash and cash equivalents at beginning of year	3,937	3,695	3,664
Cash and cash equivalents at end of year	$ 3,169	$ 3,937	$ 3,695