Stock Incentive Plans (Details) (USD $)	3 Months Ended		6 Months Ended				6 Months Ended			6 Months Ended		6 Months Ended								6 Months Ended							0 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Restricted common stock	Dec. 31, 2013 Restricted common stock	Jun. 30, 2014 Restricted common stock and restricted stock units	Jun. 30, 2014 Performance-based restricted common stock and performance-based restricted stock units	Jun. 30, 2014 Performance-based restricted common stock	Jun. 30, 2014 Performance-based restricted stock units	Dec. 31, 2013 Performance-based restricted stock units	Jun. 30, 2014 Performance-based restricted stock units Vest on February 1, 2017, performance level one	Jun. 30, 2014 Performance-based restricted stock units Vest on February 1, 2017, performance level one Change in control	Jun. 30, 2014 Performance-based restricted stock units Vest on February 1, 2017, performance level two	Jun. 30, 2014 Performance-based restricted stock units Vest on February 1, 2017, performance level three	Jun. 30, 2014 Performance-based restricted stock units Vest on February 1, 2017, performance level four	Jun. 30, 2014 Performance-based restricted stock units Vest on February 1, 2017, performance level five	Jun. 30, 2014 Employee Stock Plan, 2005 Plan	May 21, 2014 Employee Stock Plan, 2005 Plan	Jun. 30, 2014 Employee Stock Plan, 2005 Plan Restricted common stock	Jun. 30, 2014 Employee Stock Plan, 2005 Plan Restricted common stock Shares vesting in December 2014	Jun. 30, 2014 Employee Stock Plan, 2005 Plan Restricted common stock Shares vesting in December 2015	Jun. 30, 2014 Employee Stock Plan, 2005 Plan Restricted common stock Shares vesting in December 2016	Jun. 30, 2014 Employee Stock Plan, 2005 Plan Performance-based restricted stock units	Jun. 30, 2014 Directors Stock Plan, 2007 Plan Restricted common stock	Jun. 30, 2014 Directors Stock Plan, 2007 Plan Restricted common stock Vesting in February 2017	May 21, 2014 Employee Stock Plan, 2014 Plan	Jun. 30, 2014 Employee Stock Plan, 2014 Plan
Stock Incentive Plans
Restricted common stock granted (in shares)					429,346					395,900										396,840	128,830	129,430	130,630	395,900	32,506
Vested (in shares)					26,668
Forfeited (in shares)					18,326					15,700										7,950
Vesting percentage																										100.00%
Granted (in dollars per share)					$ 12.63					$ 12.14
Outstanding (in shares)					1,165,996	781,644				789,300	409,100													387,800	28,148
Share of common stock to be paid for each restricted stock unit																								1
Shares to be issued on vest date as percentage of units granted based on actual performance												125.00%		100.00%	75.00%	50.00%	0.00%
Shares to be issued on vesting date as a percentage of units granted in the event of change in control													100.00%
Additional shares authorized for future grants																											3,250,000
Shares available for future grants																		0	507,925									3,757,925
Stock-based compensation expense, net of taxes	$ 1,400,000	$ 1,100,000	$ 2,800,000	$ 2,200,000
Stock-based compensation expense, taxes	790,000	613,000	1,500,000	1,200,000
Pre-tax compensation cost related to share-based compensation awards not yet recognized							14,700,000
Pre-tax compensation cost, weighted average recognition period							2 years 1 month 6 days
Pre-tax compensation cost related to non-vested performance-based stock awards and units								$ 1,800,000
Restricted shares or units for which compensation cost will be excluded until the achievement of the performance conditions become probable									65,000	100,375