Earnings per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Earnings per Share
Income from continuing operations	$ 12,504		$ 12,448		$ 38,533		$ 36,914
Less net income allocated to non-controlling interests	(9)		(48)		(30)		(144)
Less net income allocated to participating securities:
Nonforfeitable dividends on participating securities	(94)		(85)		(279)		(259)
Total net income allocated to participating securities	(94)		(85)		(279)		(259)
Less net income allocated to preferred stockholders:
Preferred stock dividends	(818)		(818)		(2,454)		(4,694)
Preferred stock redemption charge							(3,566)
Total net income allocated to preferred stockholders	(818)		(818)		(2,454)		(8,260)
Income from continuing operations available to common stockholders	11,583		11,497		35,770		28,251
Discontinued operations:
Loss from discontinued operations			(25)				(75)
Gain on sale of assets, net					16
Net (loss) gain from discontinued operations			(25)		16		(75)
Net income available to common stockholders	11,583		11,472		35,786		28,176
Net income for diluted net income per share	$ 11,583		$ 11,472		$ 35,786		$ 28,176
Shares for basic net income per share	30,253		30,137		30,219		28,874
Effect of dilutive securities:
Stock options (in shares)	40		19		44		28
Shares for diluted net income per share	30,293		30,156		30,263		28,902
Basic net income per share (in dollars per share)	$ 0.38	[1]	$ 0.38	[1]	$ 1.18	[1]	$ 0.98	[1]
Diluted net income per share (in dollars per share)	$ 0.38	[1],[2]	$ 0.38	[1],[2]	$ 1.18	[1],[2]	$ 0.97	[1],[2]

[1] NOTE: Computations of per share amounts from continuing operations, discontinued operations and net income are made independently. Therefore, the sum of per share amounts from continuing operations and discontinued operations may not agree with the per share amounts from net income available to common stockholders.

[2] For the three and nine months ended September 30, 2012 and 2011, the Series C Cumulative Convertible Preferred Stock, the participating securities and the non-controlling interest have been excluded from the computation of diluted net income per share as such inclusion would be anti-dilutive.