Stock-Based Compensation Restricted Stock Units (Details) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015 USD ($) shares	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) years shares	Sep. 30, 2014 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incentive shares granted				379,000
Incentive shares ouststanding Aggregate Intrinsic Value (in millions) | $		$ 19.5		$ 19.5
Director restricted stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense | $		0.4	$ 0.6	1.3	$ 1.6
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs | $		5.2		5.2
Compensation Expense | $		$ 0.9	$ 0.8	$ 2.6	$ 2.2
Incentive share awards outstanding at beginning of period				593,613
Incentive shares granted				252,629
Incentive share awards vested				(285,495)
Incentive share awards canceled				(15,083)
Incentive shares outstanding at end of period		545,664		545,664
Incentive share awards outstanding Weighted Average Contractual Term (in years)				1 year 6 months
Incentive shares ouststanding Aggregate Intrinsic Value (in millions) | $		$ 7.8		$ 7.8
Vested and expected to vest at June 30, 2015	[1]	518,381		518,381
Vested and expected to vest Weighted Average Contractual Term (in years) | years	[1]			0.00
Vested and expected to vest Aggregate Intrinsic Value (in millions) | $	[1]			$ 7.4
Weighted-average period of years costs are expected to be recognied over				1 year 6 months
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs | $		$ 1.2		$ 1.2
Incentive share awards canceled				(14,544)
Incentive shares outstanding at end of period		282,701		282,701
Weighted-average period of years costs are expected to be recognied over				2 years 3 months
Director [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs | $		$ 2.2		$ 2.2
Incentive share awards outstanding at beginning of period				453,146
Incentive shares granted				69,744
Weighted-average period of years costs are expected to be recognied over				1 year 3 months 18 days
Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense | $				$ 0.5

[1] Incentive shares expected to vest based upon historical forfeiture rate