Earnings per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Earnings per Share
Income from continuing operations	$ 12,947		$ 12,273
Less income allocated to non-controlling interests	(11)		(48)
Less income allocated to participating securities
Non-forfeitable dividends on participating securities	(94)		(89)
Total income allocated to participating securities	(94)		(89)
Less net income allocated to preferred stockholders:
Preferred stock dividends	(818)		(3,058)
Preferred stock redemption charge			(3,566)
Total net income allocated to preferred stockholders	(818)		(6,624)
Income from continuing operations allocable to common stockholders	12,024		5,512
Discontinued operations:
Loss from discontinued operations	(31)		(119)
Gain on sale of assets, net	16
Net loss from discontinued operations	(15)		(119)
Net income available to common stockholders	12,009		5,393
Net income for diluted net income per share (in dollars per share)	$ 12,009		$ 5,393
Shares for basic net income per share	30,189		26,310
Effect of dilutive securities:
Stock options (in shares)	45		30
Shares for diluted net income per share	30,234		26,340
Basic net income per common share	$ 0.40	[1]	$ 0.20	[1]
Diluted net income per common share	$ 0.40	[1]	$ 0.20	[1]

[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.