Stock-Based Compensation Restricted Stock Units (Details) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incentive shares granted	494,000
Incentive shares ouststanding Aggregate Intrinsic Value (in millions)	$ 26.2
Director restricted stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	1.0
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	1.4
Incentive share awards outstanding at January 1, 2014	752,595
Incentive shares granted	146,095
Incentive share awards vested	(287,912)
Incentive share awards cancelled	(13,456)
Incentive shares outstanding at March 31, 2014	597,322
Incentive share awards outstanding Weighted Average Contractual Term (in years)	1 year 3 months 18 days
Incentive shares ouststanding Aggregate Intrinsic Value (in millions)	9.0
Vested and expected to vest at March 31, 2014	567,000
Vested and expected to vest Weighted Average Contractual Term (in years)	0.00
Vested and expected to vest Aggregate Intrinsic Value (in millions)	$ 8.5
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incentive share awards cancelled	(11,021)
Incentive shares outstanding at March 31, 2014	463,146
Director [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incentive share awards outstanding at January 1, 2014	512,085
Incentive shares granted	122,649
Chief Executive Officer [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incentive shares outstanding at March 31, 2014	300,000