Equity Incentive Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended		6 Months Ended
	May 31, 2016	Jul. 31, 2015	Jul. 31, 2012	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Equity Incentive Plan
Maximum number of common shares available for issuance (in shares)				7,500,000		7,500,000
Summary of non-vested shares/units
Granted (in shares)						2,554
Weighted Average Grant Date Fair Value
Granted (in dollars per share)						$ 22.26
Other Disclosures
Share-based compensation expense						$ (57)	$ (66)
Common shares available for future grant (in shares)				4,099,523		4,099,523
Restricted share awards
Summary of non-vested shares/units
Unvested at the beginning of the period (in shares)						540,885
Granted (in shares)						442,550
Vested (in shares)						(153,754)
Forfeited (in shares)						(286,189)
Unvested at the end of the period (in shares)				543,492		543,492
Weighted Average Grant Date Fair Value
Unvested at the beginning of the period (in dollars per share)						$ 26.73
Granted (in dollars per share)						19.89
Vested (in dollars per share)						23.69
Forfeited (in dollars per share)						23.73
Unvested at the end of the period (in dollars per share)				$ 23.60		$ 23.60
Other Disclosures
Share-based compensation expense				$ 1,300	$ 2,600	$ 3,400	5,600
Total unrecognized compensation costs				$ 12,100		$ 12,100
Weighted-average period of recognition of unrecognized share-based compensation expense						2 years 8 months 1 day
Total fair value of shares vested						$ 3,100
2012 Performance Shares
Summary of non-vested shares/units
Unvested at the end of the period (in shares)				286,000		286,000
Other Disclosures
Vesting period			4 years
Performance-based vesting period			3 years
Time-based vesting period			1 year
Restricted shares issued upon conversion of performance units (in shares)		838,934
2016 Performance Shares
Summary of non-vested shares/units
Granted (in shares)	280,000
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 10.31
Other Disclosures
Vesting period	4 years
Performance-based vesting period	3 years
Time-based vesting period	1 year
Vesting percentage upon satisfaction of performance-based vesting period	50.00%
Vesting percentage upon satisfaction of time-based vesting period	50.00%
Fair value assumptions, risk free interest rate	1.05%
Fair value assumptions, expected volatility rate	23.82%
Percentage of grant date fair value to be recognized over three years	50.00%
Employee service share based compensation cost period of recognition	3 years
Percentage of grant date fair value to be recognized over four years	50.00%
Employee service share based compensation cost period of recognition	4 years
Performance Units
Other Disclosures
Share-based compensation expense				$ (1,900)	$ 1,100	$ (1,400)	$ 2,200
Total unrecognized compensation costs				$ 2,900		$ 2,900
Weighted-average period of recognition of unrecognized share-based compensation expense						3 years 3 months 18 days
President and Chief Executive Officer | Restricted share awards
Summary of non-vested shares/units
Forfeited (in shares)	(285,926)
Other Disclosures
Share-based compensation expense	$ (500)
President and Chief Executive Officer | 2012 Performance Shares
Summary of non-vested shares/units
Forfeited (in shares)	(133,467)
President and Chief Executive Officer | Performance Units
Other Disclosures
Share-based compensation expense	$ (2,300)
Minimum | 2016 Performance Shares
Other Disclosures
Percentage of performance units that will convert into restricted shares	25.00%
Maximum | 2016 Performance Shares
Other Disclosures
Percentage of performance units that will convert into restricted shares	150.00%