Condensed Financial Information of Parent (Details) (USD $) In Thousands, unless otherwise specified	0 Months Ended	3 Months Ended								12 Months Ended
	Mar. 28, 2013	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets
Cash and cash equivalents		$ 13,057	$ 17,167	$ 20,416	$ 13,894	$ 16,570	$ 20,117	$ 18,683	$ 16,523	$ 13,057	$ 16,570
Investments		461,180	472,660	502,015	488,553	475,101	490,151	464,999	437,160	461,180	475,101
Premises and equipment		22,619				23,616				22,619	23,616
Goodwill		29,805				29,805				29,805	29,805
Other assets		22,246				27,616				22,246	27,616
Total assets		1,482,131	1,488,637	1,504,080	1,466,117	1,463,963	1,464,749	1,444,496	1,416,787	1,482,131	1,463,963
Liabilities and shareholders' equity
Other liabilities		15,842	15,489	14,675	14,212	14,341	13,853	13,734	16,070	15,842	14,341
Total liabilities		1,320,577				1,317,865				1,320,577	1,317,865
Shareholders' equity
Common stock		107				106				107	106
Additional paid-in capital		59,282				58,395				59,282	58,395
Retained earnings		99,816				94,000				99,816	94,000
Accumulated other comprehensive income (loss)
Net unrealized gain on available for sale securities, net of tax		2,522				(6,591)				2,522	(6,591)
Total shareholders' equity		161,554	159,190	157,449	152,416	146,098	146,653	145,972	163,671	161,554	146,098	156,323	150,858
Total liabilities and shareholders' equity		1,482,131	1,488,637	1,504,080	1,466,117	1,463,963	1,464,749	1,444,496	1,416,787	1,482,131	1,463,963
Statements of Income
Net securities gains										1,155	1,087	1,968
Loss before income taxes and Bank earnings		4,474	5,508	4,902	4,391	4,441	4,320	4,067	3,562	19,275	16,390	16,059
Applicable tax expense		1,048	1,400	1,155	963	939	955	825	706	4,566	3,425	3,371
Equity in earnings of Bank
Net income		3,426	4,108	3,747	3,428	3,502	3,365	3,242	2,856	14,709	12,965	12,688
Cash flows from operating activities
Net income		3,426	4,108	3,747	3,428	3,502	3,365	3,242	2,856	14,709	12,965	12,688
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation										1,663	1,727	1,314
Equity compensation expense										431	214	85
Net gain on sale or call of securities										(1,155)	(1,087)	(1,968)
Net decrease in other assets and accrued interest										676	1,557	756
Increase (decrease) in other liabilities										378	1,370	1,631
Net cash provided by operating activities										20,463	24,984	25,023
Cash flows from investing activities
Capital expenditures										(1,909)	(2,363)	(1,726)
Net cash used in investing activities										(16,751)	(75,957)	(19,270)
Cash flows from financing activities
Repurchase of preferred stock										0	(12,500)	0
Proceeds from sale of common stock	11,649									457	11,973	499
Dividends paid										(8,893)	(8,657)	(8,310)
Net cash used in financing activities										(7,225)	52,585	(4,910)
Net increase (decrease) in cash and cash equivalents										(3,513)	1,612	843
Cash and cash equivalents at beginning of year					16,570				14,958	16,570	14,958	14,115
Cash and cash equivalents at end of year		13,057				16,570				13,057	16,570	14,958
Parent Company
Assets
Cash and cash equivalents		522				1,113				522	1,113
Dividends receivable		2,500				1,500				2,500	1,500
Investments		528				543				528	543
Investment in subsidiary		132,399				117,391				132,399	117,391
Premises and equipment		24				32				24	32
Goodwill		27,559				27,559				27,559	27,559
Other assets		302				203				302	203
Total assets		163,834				148,341				163,834	148,341
Liabilities and shareholders' equity
Dividends payable		2,252				2,134				2,252	2,134
Other liabilities		28				109				28	109
Total liabilities		2,280				2,243				2,280	2,243
Shareholders' equity
Common stock		107				106				107	106
Additional paid-in capital		59,282				58,395				59,282	58,395
Retained earnings		102,125				87,523				102,125	87,523
Accumulated other comprehensive income (loss)
Net unrealized gain on available for sale securities, net of tax		40				74				40	74
Total accumulated other comprehensive income		40				74				40	74
Total shareholders' equity		161,554				146,098				161,554	146,098
Total liabilities and shareholders' equity		163,834				148,341				163,834	148,341
Statements of Income
Interest and dividends on investments										15	10	10
Net securities gains										38	0	0
Total income										53	10	10
Occupancy expense										12	11	8
Other operating expense										604	362	218
Total expense										616	373	226
Loss before income taxes and Bank earnings										(563)	(363)	(216)
Applicable tax expense										(200)	(128)	(76)
Loss before Bank earnings										(363)	(235)	(140)
Equity in earnings of Bank
Remitted										8,850	7,096	9,694
Unremitted										6,222	6,104	3,134
Net income										14,709	12,965	12,688
Cash flows from operating activities
Net income										14,709	12,965	12,688
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation										9	11	8
Equity compensation expense										431	214	85
Net gain on sale or call of securities										(38)	0	0
Net decrease in other assets and accrued interest										(98)	(132)	(15)
(Increase) decrease in dividend receivable										(1,050)	400	0
Increase (decrease) in other liabilities										105	258	(5)
Unremitted										(6,222)	(6,104)	(3,134)
Net cash provided by operating activities										7,846	7,612	9,627
Cash flows from investing activities
Capital expenditures										(1)	0	(25)
Net cash used in investing activities										(1)	0	(25)
Cash flows from financing activities
Repurchase of preferred stock										0	(12,500)	0
Proceeds from sale of common stock										457	11,973	499
Dividends paid										(8,893)	(8,657)	(8,310)
Net cash used in financing activities										(8,436)	(9,184)	(7,811)
Net increase (decrease) in cash and cash equivalents										(591)	(1,572)	1,791
Cash and cash equivalents at beginning of year					1,113				2,685	1,113	2,685	894
Cash and cash equivalents at end of year		$ 522				$ 1,113				$ 522	$ 1,113	$ 2,685