Stock Incentive Plans (Details) (USD $)	9 Months Ended		3 Months Ended			9 Months Ended														12 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Restricted common stock	Sep. 30, 2012 Restricted common stock	Mar. 31, 2012 Restricted common stock	Sep. 30, 2013 Restricted common stock	Sep. 30, 2012 Restricted common stock	Sep. 30, 2013 Performance-based restricted stock awards or units Officers Vest on February 1, 2016, performance level one	Sep. 30, 2013 Performance-based restricted stock awards or units Officers Vest on February 1, 2016, performance level one Change in control	Sep. 30, 2013 Performance-based restricted stock awards or units Officers Vest on February 1, 2016, performance level two	Sep. 30, 2013 Performance-based restricted stock awards or units Officers Vest on February 1, 2016, performance level three	Sep. 30, 2013 Performance-based restricted stock awards or units Officers Vest on February 1, 2016, performance level four	Sep. 30, 2013 Employee Stock Plan, 2005 Plan Vesting in December 2013	Sep. 30, 2013 Employee Stock Plan, 2005 Plan Vesting in December 2014	Sep. 30, 2013 Employee Stock Plan, 2005 Plan Vesting in December 2015	Sep. 30, 2013 Employee Stock Plan, 2005 Plan Restricted common stock	Sep. 30, 2013 Employee Stock Plan, 2005 Plan Restricted common stock Shares vesting one-third per year beginning in December 2013	Sep. 30, 2013 Employee Stock Plan, 2005 Plan Restricted common stock Shares vesting one-third per year beginning in January 2014	Sep. 30, 2013 Employee Stock Plan, 2005 Plan Performance-based restricted stock awards or units	Dec. 31, 2011 Employee Stock Plan, 2005 Plan Performance-based restricted stock awards or units	Mar. 31, 2013 Employee Stock Plan, 2005 Plan Performance-based restricted stock awards or units Officers	Sep. 30, 2013 Employee Stock Plan, 2005 Plan Performance-based restricted stock awards or units Officers	Sep. 30, 2013 Directors Stock Plan, 2007 Plan Restricted common stock	Sep. 30, 2013 Directors Stock Plan, 2007 Plan Restricted common stock Vesting in January 2016
Stock Incentive Plans
Restricted common stock granted (in shares)	536,110												1,000	1,500	2,500	494,420	467,070	6,000	103,975	65,000	432,300		41,690
Vesting percentage																	33.00%	33.00%						100.00%
Stock-based compensation expense, net of taxes			$ 1,200,000	$ 978,000		$ 3,400,000	$ 2,400,000
Stock-based compensation expense, taxes			636,000	533,000		1,900,000	1,300,000
Pre-tax compensation cost related to non-vested restricted stock awards not yet recognized			12,000,000			12,000,000
Pre-tax compensation cost related to non-vested performance-based stock awards and units			1,800,000			1,800,000
Pre-tax compensation cost related to restricted stock awards, weighted average recognition period						2 years
Restricted stock, shares forfeited	90,306															16,350
Awards outstanding (in shares)	1,295,156	1,146,657																				415,900	36,020
Granted (in dollars per share)	$ 9.70																				$ 9.22
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								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%
Stock-based compensation expense reversed					569,000
Stock-based compensation expense, taxes reversed					$ 310,000