Parent Company Financial Statements (Statements of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:
Net income	$ 36,153	$ 35,074	$ 29,724
Adjustments to reconcile net income to net cash provided by operating activities:
Decrease (increase) in other assets	2,589	(7,987)	(2,804)
Net cash provided by operating activities	80,850	5,467	37,199
Cash flows from investing activities:
Repayment of investment in capital trust	310	0	0
Net cash (used in) provided by investing activities	(184,062)	25,337	(158,576)
Cash flows from financing activities:
Proceeds from issuance of common stock under dividend reinvestment plan	0	0	754
Proceeds from stock option exercises and issuance of other equity instruments	3,681	1,257	885
Tax benefit from stock option exercises and other equity instruments	570	210	115
Redemption of junior subordinated debentures	(10,310)	0	0
Cash dividends paid	(16,628)	(15,133)	(14,205)
Net cash provided by (used in) financing activities	95,879	(25,174)	115,661
Net (decrease) increase in cash and cash equivalents	(7,333)	5,630	(5,716)
Cash and cash equivalents at beginning of year	92,650	87,020	92,736
Cash and cash equivalents at end of year	85,317	92,650	87,020
Parent Company [Member]
Cash flows from operating activities:
Net income	36,153	35,074	29,724
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of subsidiaries	(12,899)	(20,177)	(16,557)
Increase in dividend receivable	(408)	(298)	(660)
Decrease (increase) in other assets	397	77	(246)
(Decrease) increase in accrued expenses and other liabilities	(621)	(215)	281
Other, net	(214)	(237)	(115)
Net cash provided by operating activities	22,408	14,224	12,427
Cash flows from investing activities:
Repayment of investment in capital trust	310	0	0
Net cash (used in) provided by investing activities	310	0	0
Cash flows from financing activities:
Issuance of treasury stock, including net deferred compensation plan activity	30	0	0
Proceeds from issuance of common stock under dividend reinvestment plan	0	0	754
Proceeds from stock option exercises and issuance of other equity instruments	3,651	1,257	885
Tax benefit from stock option exercises and other equity instruments	570	210	115
Redemption of junior subordinated debentures	(10,310)	0	0
Cash dividends paid	(16,628)	(15,133)	(14,205)
Net cash provided by (used in) financing activities	(22,687)	(13,666)	(12,451)
Net (decrease) increase in cash and cash equivalents	31	558	(24)
Cash and cash equivalents at beginning of year	3,664	3,106	3,130
Cash and cash equivalents at end of year	$ 3,695	$ 3,664	$ 3,106