Equity Incentive Plan (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating Partnership Units
Restricted Awards
Granted (in shares)	25,883
Forfeited (in shares)	(1,491)
Unvested balance at the end of the period (in shares)	7,138
Weighted Average Fair Value at Grant Date
Granted (in dollars per share)	$ 15.98
Total grant date fair value of operating partnership units	$ 0.4
Compensation cost not yet recognized
Unearned compensation	0.1
Vested shares outstanding	17,254
Operating Partnership Units | Weighted average
Compensation cost not yet recognized
Vesting period	8 months 12 days
2010 Plan
Equity Incentive Plan
Shares reserved for issuance	3,000,000
Shares of common stock that remained available for issuance pursuant to the 2010 Plan	993,033
2010 Plan | Stock options
Number of Shares Subject to Option
Options outstanding at the beginning of the period (in shares)	998,051	587,555
Granted (in shares)	236,893	543,380	587,555
Forfeited (in shares)	(119,723)	(122,848)
Expired (in shares)	(156)	(8,074)
Exercised (in shares)	(97,870)	(1,962)
Options outstanding at the end of the period (in shares)	1,017,195	998,051	587,555
Exercisable at the end of the period (in shares)	287,036	130,942
Weighted Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share)	$ 15.63	$ 16.00
Granted (in dollars per share)	$ 23.87	$ 15.27	$ 16.00
Forfeited (in dollars per share)	$ 16.62	$ 15.80
Expired (in dollars per share)	$ 16.00	$ 16.00
Exercised (in dollars per share)	$ 16.04	$ 16.00
Options outstanding at the end of the period (in dollars per share)	$ 17.25	$ 15.63	$ 16.00
Exercisable at the end of the period (in dollars per share)	$ 15.74	$ 16.00
Weighted Average Remaining Contractual Term
Options outstanding at the end of the period	8 years 2 months 12 days	8 years 10 months 24 days	9 years 8 months 12 days
Exercisable at the end of the period	7 years 10 months 24 days	8 years 8 months 12 days
Aggregate Intrinsic Value
Exercised	0.8
Outstanding at the end of the period	10.6	2.2
Exercisable at the end of the period	3.4	0.2
Number of Shares Subject to Option
Unvested balance at the beginning of the period (in shares)	867,109	587,555
Granted (in shares)	236,893	543,380	587,555
Forfeited (in shares)	(119,723)	(122,848)
Vested (in shares)	(254,120)	(140,978)
Unvested balance at the end of the period (in shares)	730,159	867,109	587,555
Weighted Average Fair Value at Grant
Unvested balance at the beginning of the period (in dollars per share)	$ 4.92	$ 4.95
Granted (in dollars per share)	$ 7.76	$ 4.89	$ 4.95
Forfeited (in dollars per share)	$ 5.24	$ 4.93
Vested (in dollars per share)	$ 4.96	$ 4.92
Unvested balance at the end of the period (in dollars per share)	$ 5.70	$ 4.92	$ 4.95
Assumptions used to value the stock options granted
Expected term	6 years 3 months	6 years 3 months	6 years 3 months
Expected volatility (as a percent)	44.08%	43.07%	43.59%
Expected annual dividend (as a percent)	3.00%	3.41%	3.25%
Risk-free rate (as a percent)	1.56%	2.76%	1.33%
Compensation cost not yet recognized
Unearned compensation	3.3
2010 Plan | Stock options | Weighted average
Compensation cost not yet recognized
Vesting period	2 years 3 months 18 days
2010 Plan | Stock options | Maximum
Aggregate Intrinsic Value
Exercised		0.1
2010 Plan | Restricted Awards
Restricted Awards
Unvested balance at the beginning of the period (in shares)	343,231	195,437
Granted (in shares)	412,780	273,473	195,437
Forfeited (in shares)	(48,599)	(51,213)
Vested (in shares)	(108,717)	(74,466)
Unvested balance at the end of the period (in shares)	598,695	343,231	195,437
Weighted Average Fair Value at Grant Date
Unvested balance at the beginning of the period (in dollars per share)	$ 15.35	$ 15.98
Granted (in dollars per share)	$ 24.59	$ 15.19	$ 15.98
Forfeited (in dollars per share)	$ 18.26	$ 15.81
Vested (in dollars per share)	$ 15.46	$ 16.10
Unvested balance at the end of the period (in dollars per share)	$ 21.37	$ 15.35	$ 15.98
Compensation cost not yet recognized
Unearned compensation	9.7
2010 Plan | Restricted Awards | Weighted average
Compensation cost not yet recognized
Vesting period	2 years 3 months 18 days
2010 Plan | Restricted awards
Restricted Awards
Grant date value	9.9	4.0	3.0
Number of awards granted under new employment agreements (in shares)	176,630
Granted (in shares)	405,608	263,393	185,437
2010 Plan | RSUs
Restricted Awards
Grant date value	$ 0.2	$ 0.2	$ 0.2
Granted (in shares)	7,172	10,080	10,000