Stock Options and Restricted Shares (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for Stock Option Plan	5,000,000
Weighted Average Exercise Price [Roll Forward]
Granted, weighted average exercise price (in dollars per share)	$ 5.41	$ 4.72	$ 3.99
Weighted Average Grant Date Fair Value [Roll Forward]
Granted (in dollars per share)	$ 11.10	$ 10.77	$ 8.45
Shares available for grant, balance at end of period (in shares)	703,000
Unrecognized compensation costs for stock options	$ 1,795,000
Expected forfeiture rate for key employees (in hundredths)	10.00%
Expected forfeiture rate for non-key employees (in hundredths)	15.00%
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding as of end of period (in shares)	1,143,000
Options Outstanding, Weighted Average Remaining Contractual Life	6 years 1 month 6 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 10.38
Options Exercisable as of end of period (in shares)	661,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 8.51
$0.78 to $6.39 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 0.78
Exercise price range, upper range limit (in dollars per share)	$ 6.39
Options Outstanding as of end of period (in shares)	123,000
Options Outstanding, Weighted Average Remaining Contractual Life	3 years 9 months 18 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 4.50
Options Exercisable as of end of period (in shares)	123,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 4.50
$6.40 to $7.88 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 6.40
Exercise price range, upper range limit (in dollars per share)	$ 7.88
Options Outstanding as of end of period (in shares)	131,000
Options Outstanding, Weighted Average Remaining Contractual Life	1 year 9 months 18 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 7.12
Options Exercisable as of end of period (in shares)	131,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 7.12
$7.89 to $9.41 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 7.89
Exercise price range, upper range limit (in dollars per share)	$ 9.41
Options Outstanding as of end of period (in shares)	53,000
Options Outstanding, Weighted Average Remaining Contractual Life	4 years 2 months 12 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 9.38
Options Exercisable as of end of period (in shares)	53,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 9.46
$9.42 to $9.46 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 9.42
Exercise price range, upper range limit (in dollars per share)	$ 9.46
Options Outstanding as of end of period (in shares)	119,000
Options Outstanding, Weighted Average Remaining Contractual Life	2 years 1 month 6 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 9.46
Options Exercisable as of end of period (in shares)	119,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 7.14
$9.47 to $10.89 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 9.47
Exercise price range, upper range limit (in dollars per share)	$ 10.89
Options Outstanding as of end of period (in shares)	137,000
Options Outstanding, Weighted Average Remaining Contractual Life	3 years 10 months 24 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 10.08
Options Exercisable as of end of period (in shares)	137,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 10.08
$10.90 to $11.63 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 10.90
Exercise price range, upper range limit (in dollars per share)	$ 11.63
Options Outstanding as of end of period (in shares)	150,000
Options Outstanding, Weighted Average Remaining Contractual Life	9 years 1 month 6 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 11.23
Options Exercisable as of end of period (in shares)	39,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 11.46
$11.64 to $12.03 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 11.64
Exercise price range, upper range limit (in dollars per share)	$ 12.03
Options Outstanding as of end of period (in shares)	160,000
Options Outstanding, Weighted Average Remaining Contractual Life	8 years 8 months 12 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 11.89
Options Exercisable as of end of period (in shares)	59,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 11.72
$12.04 to $15.03 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 12.04
Exercise price range, upper range limit (in dollars per share)	$ 15.03
Options Outstanding as of end of period (in shares)	270,000
Options Outstanding, Weighted Average Remaining Contractual Life	9 years 1 month 6 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 14.03
Options Exercisable as of end of period (in shares)	0
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 0
Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of successive periods to awards vesting	5
Escalation (in dollars per share)	$ 1
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Terms of award (in years)	P10Y
Vesting period, incentive stock options	4 years
Award vesting period, nonqualified stock options	1 year
Number of months after employment until the options are terminated	3 months
Vesting period for options	1 year
Forfeiture rate on options granted (in hundredths)	0.00%
Plan Options Outstanding [Roll Forward]
Balance at beginning of year (in shares)	801,000	837,000	1,030,000
Reserved (in shares)	0	0	0
Granted (in shares)	500,000	70,000	60,000
Exercised (in shares)	(158,000)	(87,000)	(239,000)
Forfeited (in shares)	0	0	0
Expired (in shares)	0	(19,000)	(14,000)
Balance at end of year (in shares)	1,143,000	801,000	837,000
Weighted Average Exercise Price [Roll Forward]
Balance at beginning of year, weighted average exercise price (in dollars per share)	$ 7.38	$ 6.62	$ 6.06
Reserved, weighted average exercise price (in dollars per share)	$ 0	$ 0	$ 0
Granted, weighted average exercise price (in dollars per share)	$ 12.89	$ 11.72	$ 9.84
Exercised, weighted average exercise price (in dollars per share)	$ 3.10	$ 4.00	$ 4.79
Forfeited, weighted average exercise price (in dollars per share)	$ 0	$ 0	$ 0
Expired, weighted average exercise price (in dollars per share)	$ 0	$ 5.45	$ 9.95
Balance at end of period, weighted average exercise price (in dollars per share)	$ 10.38	$ 7.38	$ 6.62
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding balance, aggregate intrinsic value	6,197,000
Exercisable at end of period (in shares)	661,000
Exercisable, weighted average exercise price (in dollars per share)	$ 8.51
Exercisable, intrinsic value at end of period	4,817,000
Exercise price, reserved (in dollars per share)	$ 0	$ 0	$ 0
Exercise price, granted (in dollars per share)		$ 11.72
Exercise price, forfeited (in dollars per share)	$ 0	$ 0	$ 0
Exercise price, expired (in dollars per share)	$ 0
Options, exercisable, weighted average remaining contractual term	3 years 9 months 18 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value	1,464,000	677,000	1,353,000
Weighted Average Grant Date Fair Value [Roll Forward]
Shares available for grant, balance at beginning (in shares)	4,327,000	3,878,000	3,424,000
Reserved (in shares)	(1,900,000)	500,000	500,000
Granted (in shares)	(500,000)	(70,000)	(60,000)
Exercised (in shares)	0	0	0
Forfeited (in shares)	0	0	0
Expired (in shares)	0	19,000	14,000
Shares available for grant, balance at end of period (in shares)	1,927,000	4,327,000	3,878,000
Weighted average period for recognizing unrecognized compensation costs	1 year 11 months 19 days
Stock Options [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercise price, beginning balance (in dollar per share)	$ 0.78	$ 0.78	$ 0.78
Exercise price, granted (in dollars per share)	$ 11.03		$ 9.61
Exercise price, exercised (in dollars per share)	$ 0.84	$ 0.84	$ 0.84
Exercise price, expired (in dollars per share)		$ 0.84	$ 9.46
Exercise price, beginning balance (in dollar per share)	$ 0.78	$ 0.78	$ 0.78
Stock Options [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercise price, beginning balance (in dollar per share)	$ 11.72	$ 10.98	$ 10.89
Exercise price, granted (in dollars per share)	$ 15.03		$ 10.98
Exercise price, exercised (in dollars per share)	$ 10.28	$ 9.46	$ 9.58
Exercise price, expired (in dollars per share)		$ 9.46	$ 10.28
Exercise price, beginning balance (in dollar per share)	$ 15.03	$ 11.72	$ 10.98
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for options	1 year
Share Outstanding [Roll Forward]
Balance at beginning of year (in shares)	567,000	463,000	445,000
Granted (in shares)	245,000	274,000	260,000
Vested (in shares)	(167,000)	(132,000)	(133,000)
Forfeited (in shares)	(32,000)	(38,000)	(109,000)
Expired	0	0	0
Balance at end of period (in shares)	613,000	567,000	463,000
Weighted Average Grant Date Fair Value [Roll Forward]
Balance at beginning of year (in dollars per share)	$ 9.43	$ 8.49	$ 8.07
Granted (in dollars per share)	$ 11.10	$ 10.77	$ 8.45
Vested (in dollars per share)	$ 8.12	$ 8.72	$ 7.00
Forfeited (in dollars per share)	$ 10.67	$ 10.05	$ 8.50
Expired (in dollars per share)	$ 0	$ 0	$ 0
Balance at beginning of year (in dollars per share)	$ 10.39	$ 9.43	$ 8.49
Shares available for grant, balance at end of period (in shares)	1,224,000
Unrecognized compensation costs for restricted shares	$ 1,807,000
Weighted average period for recognizing unrecognized compensation costs	1 year 1 month 24 days
Expected forfeiture rate for directors (in hundredths)	0.00%
Expected forfeiture rate for key employees (in hundredths)	10.00%
Expected forfeiture rate for non-key employees (in hundredths)	15.00%
Restricted Stock [Member] | Director [Member]
Weighted Average Grant Date Fair Value [Roll Forward]
Number of Directors Shares Granted	1