Stock-Based Compensation Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Restricted and performance-based stock, weighted average grant date fair value per share [Roll Forward]
Compensation expense, gross	$ 2,927	$ 2,397
Stock Options [Member]
Options, shares [Roll Forward]
Outstanding, beginning of period (in shares)	9,875
Expired (in shares)	0
Exercised (in shares)	(9,875)
Forfeited, other (in shares)	0
Outstanding, end of period (in shares)	0		9,875
Options exercisable, end of period (in shares)	0
Options, weighted average exercise price [Roll Forward]
Outstanding, beginning of period (in dollars per share)	$ 10.99
Expired (in dollars per share)	0
Exercised (in dollars per share)	10.99
Forfeited, other (in dollars per share)	0
Outstanding, end of period (in dollars per share)	0		$ 10.99
Options exercisable, end of period (in dollars per share)	$ 0
Options, additional disclosures [Abstract]
SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2			4 months 24 days
SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2			4 months 24 days
Options exercisable, weighted average remaining contractual term, end of period
Total intrinsic value of options exercised	$ 300
Options granted (in shares)	0
Performance-based Shares [Member]
Restricted and Performance Stock Grants [Abstract]
Measuring period for performance-based shares	3 years
Award vesting rights	Selected executives and other key personnel are granted performance awards whose vesting is contingent upon meeting various performance measures with a retention feature. Performance-based shares are subject to a three-year measuring period and the achievement of performance targets and, depending upon the achievement of such performance targets, they may become vested on the third anniversary of the date of grant.
Restricted Shares [Member]
Restricted and Performance Stock Grants [Abstract]
Award vesting rights	Restricted shares granted to employees become fully vested upon the third anniversary of the date of grant; and for selected key executives, certain additional restricted share grants vest 25% upon the attainment of age 60, 25% upon the attainment of age 63 and become fully vested upon the attainment of age 65. Restricted shares granted to directors become fully vested upon the first anniversary of the date of grant.
Restricted Shares [Member] | Employees [Member]
Restricted and Performance Stock Grants [Abstract]
Estimated forfeitures (in hundredths)	5.00%
Restricted Shares [Member] | Executives [Member]
Restricted and Performance Stock Grants [Abstract]
Estimated forfeitures (in hundredths)	0.00%
Restricted Shares [Member] | Directors [Member]
Restricted and Performance Stock Grants [Abstract]
Estimated forfeitures (in hundredths)	0.00%
Restricted Shares [Member] | Age 60 [Member]
Restricted and Performance Stock Grants [Abstract]
Vesting percentage (in hundredths)	25.00%
Restricted Shares [Member] | Age 63 [Member]
Restricted and Performance Stock Grants [Abstract]
Vesting percentage (in hundredths)	25.00%
Restricted Shares [Member] | Age65 [Member]
Restricted and Performance Stock Grants [Abstract]
Vesting percentage (in hundredths)	100.00%
Restricted and Performance-based shares [Member]
Restricted and performance-based stock, shares [Roll Forward]
Beginning of period (in shares)	749,018
Granted (in shares)	7,000
Vested (in shares)	(44,293)
Forfeited (in shares)	(2,675)
End of period (in shares)	709,050		749,018
Restricted and performance-based stock, weighted average grant date fair value per share [Roll Forward]
Beginning of period (in dollars per share)	$ 24.62
Granted (in dollars per share)	35.07
Vested (in dollars per share)	34.47
Forfeited (in dollars per share)	25.00
End of period (in dollars per share)	$ 24.10		$ 24.62
Compensation expense, gross	$ 2,500	2,000
Compensation expense, net of tax	1,600	$ 1,300
Unamortized compensation expense	$ 9,700
Restricted and Performance-based shares [Member] | Employees [Member]
Restricted and performance-based stock, weighted average grant date fair value per share [Roll Forward]
Weighted average period of recognition for unrecognized compensation expense	4 years 9 months 18 days
Restricted and Performance-based shares [Member] | Directors [Member]
Restricted and performance-based stock, weighted average grant date fair value per share [Roll Forward]
Weighted average period of recognition for unrecognized compensation expense	9 months 18 days