Stock Incentive Plans (Details) (USD $)	3 Months Ended				3 Months Ended			3 Months Ended		3 Months Ended											0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Restricted common stock	Dec. 31, 2013 Restricted common stock	Mar. 31, 2014 Restricted common stock and restricted stock units	Mar. 31, 2014 Performance-based restricted common stock and performance-based restricted stock units	Mar. 31, 2014 Performance-based restricted common stock	Mar. 31, 2014 Performance-based restricted stock units	Dec. 31, 2013 Performance-based restricted stock units	Mar. 31, 2014 Performance-based restricted stock units Vest on February 1, 2017, performance level one	Mar. 31, 2014 Performance-based restricted stock units Vest on February 1, 2017, performance level one Change in control	Mar. 31, 2014 Performance-based restricted stock units Vest on February 1, 2017, performance level two	Mar. 31, 2014 Performance-based restricted stock units Vest on February 1, 2017, performance level three	Mar. 31, 2014 Performance-based restricted stock units Vest on February 1, 2017, performance level four	Mar. 31, 2014 Performance-based restricted stock units Vest on February 1, 2017, performance level five	Mar. 31, 2014 Employee Stock Plan, 2005 Plan Restricted common stock	Mar. 31, 2014 Employee Stock Plan, 2005 Plan Restricted common stock Shares vesting one-third per year beginning in December 2014	Mar. 31, 2014 Employee Stock Plan, 2005 Plan Performance-based restricted stock units	Mar. 31, 2014 Directors Stock Plan, 2007 Plan Restricted common stock	Mar. 31, 2014 Directors Stock Plan, 2007 Plan Restricted common stock Vesting in February 2017	Mar. 19, 2014 Employee Stock Plan, 2014 Plan
Stock Incentive Plans
Restricted common stock granted (in shares)			423,346					395,900								390,840		395,900	32,506
Vesting percentage																	33.33%			100.00%
Granted (in dollars per share)			$ 12.62					$ 12.14
Outstanding (in shares)			1,178,322	781,644				805,000	409,100										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
Stock-based compensation expense, net of taxes	$ 1,300,000	$ 1,100,000
Stock-based compensation expense, taxes	712,000	609,000
Pre-tax compensation cost related to share-based compensation awards not yet recognized					17,400,000
Pre-tax compensation cost, weighted average recognition period					2 years 3 months 18 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	102,275