Equity Incentive Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended				3 Months Ended		6 Months Ended
	Feb. 28, 2017	May 31, 2016	Jul. 31, 2015	Jul. 31, 2012	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Equity Incentive Plan
Maximum number of common shares available for issuance (in shares)					7,500,000		7,500,000
Other Disclosures
Share-based compensation expense							$ 0	$ (57)
Common shares available for future grant (in shares)					3,545,497		3,545,497
Restricted share awards
Summary of non-vested shares/units
Unvested at the beginning of the period (in shares)							649,447
Granted (in shares)							333,836
Vested (in shares)							(150,949)
Forfeited (in shares)							(4,791)
Unvested at the end of the period (in shares)					827,543		827,543
Weighted Average Grant Date Fair Value
Unvested at the beginning of the period (in dollars per share)							$ 23.00
Granted (in dollars per share)							23.49
Vested (in dollars per share)							23.62
Forfeited (in dollars per share)							23.25
Unvested at the end of the period (in dollars per share)					$ 23.09		$ 23.09
Other Disclosures
Share-based compensation expense					$ 2,700	$ 1,300	$ 4,700	3,400
Total unrecognized compensation costs					16,600		$ 16,600
Weighted-average period of recognition of unrecognized share-based compensation expense							2 years 7 months
Total fair value of shares vested							$ 3,200	3,100
2012 Performance Shares
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
2017 Performance Shares
Summary of non-vested shares/units
Granted (in shares)	259,000
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 14.93
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	1.57%
Fair value assumptions, expected volatility rate	25.73%
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					400	$ (1,900)	800	$ (1,400)
Total unrecognized compensation costs					$ 5,300		$ 5,300
Weighted-average period of recognition of unrecognized share-based compensation expense							2 years 11 months
President and Chief Executive Officer [Member] | Restricted share awards
Other Disclosures
Share-based compensation expense		$ 500
President and Chief Executive Officer [Member] | 2012 Performance Shares
Summary of non-vested shares/units
Forfeited (in shares)		(133,467)
President and Chief Executive Officer [Member] | Performance Units
Other Disclosures
Share-based compensation expense		$ 2,300
Minimum | 2017 Performance Shares
Other Disclosures
Percentage of performance units that will convert into restricted shares	25.00%
Maximum | 2017 Performance Shares
Other Disclosures
Percentage of performance units that will convert into restricted shares	150.00%