Stock Incentive Plans - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May. 22, 2014	May. 21, 2014
Stock Incentive Plan
Options outstanding and exercisable, intrinsic value	$ 0
Weighted average remaining contractual term	7 months
Restricted Common Stock
Stock Incentive Plan
Granted during the year (in shares)	429,752
Aggregate fair value on the vest date of restricted common stock awards, vested during the year	$ 11,700,000	$ 6,600,000	$ 9,600,000
Granted (in dollars per share)	$ 13.05	$ 12.58	$ 9.70
Stock based compensation expense, net of tax	$ 6,800,000	$ 5,600,000	$ 4,500,000
Stock based compensation expense, taxes	4,600,000	$ 3,100,000	$ 2,500,000
Nonvested awards, compensation cost not yet recognized	$ 6,300,000
Nonvested awards, compensation cost not yet recognized, period for recognition	1 year 9 months 4 days
Pretax compensation cost related to non-vested performance based stock awards and units	$ 4,500,000
Restricted Stock Units
Stock Incentive Plan
Granted during the year (in shares)	409,800
Granted (in dollars per share)	$ 12.64
Employee service share based compensation non vested performance based awards total compensation cost not yet recognized, shares or units	288,025
Restricted Stock Units | Officers
Stock Incentive Plan
Equity instruments other than options vested in period share of common stock to be paid	1
Granted during the year (in shares)	409,800	395,900	432,300
Restricted Stock Units | Officers | Change in control
Stock Incentive Plan
Granted upon change in control	100.00%
Performance-based restricted common stock
Stock Incentive Plan
Employee service share based compensation non vested performance based awards total compensation cost not yet recognized, shares or units	65,000
2014 Employee Stock Plan
Stock Incentive Plan
Number of shares authorized					3,250,000
Number of shares available for grant	3,310,991
Common stock, capital shares reserved for future issuance					3,757,925
2005 Employee Stock Plan
Stock Incentive Plan
Number of shares available for grant				0	507,925
Directors Stock Plan, 2007 Plan | Restricted Common Stock
Stock Incentive Plan
Number of shares authorized	240,080
Number of shares available for grant	49,633
Granted during the year (in shares)	28,232
Award vesting period	3 years
All stock plans other than 2014 Employee stock plan, 2005 Employee stock plan and 2007 Directors stock plan
Stock Incentive Plan
Expiration period	10 years
Minimum | Restricted Stock Units | Officers
Stock Incentive Plan
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage	0.00%
Maximum | Restricted Stock Units | Officers
Stock Incentive Plan
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage	125.00%