Stockholders' Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Reconciliation of equity attributable to company and to noncontrolling interests
Net income (loss)	$ 2,928	$ 2,011	$ 6,062	$ (3,751)
Common Stock [Member]
Reconciliation of equity attributable to company and to noncontrolling interests
Beginning Balance			779
Issuance of common stock			1
Common stock redemption			0
Stock-based compensation			0
Net income (loss)			0
Dividends to common stockholders ($0.30 per share)			0
Ending Balance	780		780
Additional Paid-In Capital [Member]
Reconciliation of equity attributable to company and to noncontrolling interests
Beginning Balance			1,894,604
Issuance of common stock			523
Common stock redemption			(45)
Stock-based compensation			1,653
Net income (loss)			0
Dividends to common stockholders ($0.30 per share)			0
Ending Balance	1,896,735		1,896,735
Accumulated Other Comprehensive Loss [Member]
Reconciliation of equity attributable to company and to noncontrolling interests
Beginning Balance			(3,332)
Issuance of common stock			0
Common stock redemption			0
Stock-based compensation			0
Net income (loss)			0
Dividends to common stockholders ($0.30 per share)			0
Ending Balance	(3,332)		(3,332)
Cumulative Net Income [Member]
Reconciliation of equity attributable to company and to noncontrolling interests
Beginning Balance			795,951
Issuance of common stock			0
Common stock redemption			0
Stock-based compensation			0
Net income (loss)			6,042
Dividends to common stockholders ($0.30 per share)			0
Ending Balance	801,993		801,993
Cumulative Dividends [Member]
Reconciliation of equity attributable to company and to noncontrolling interests
Beginning Balance			(1,683,196)
Issuance of common stock			0
Common stock redemption			0
Stock-based compensation			0
Net income (loss)			0
Dividends to common stockholders ($0.30 per share)			(46,785)
Ending Balance	(1,729,981)		(1,729,981)
Total Stockholders' Equity [Member]
Reconciliation of equity attributable to company and to noncontrolling interests
Beginning Balance			1,004,806
Issuance of common stock			524
Common stock redemption			(45)
Stock-based compensation			1,653
Net income (loss)			6,042
Dividends to common stockholders ($0.30 per share)			(46,785)
Ending Balance	$ 966,195		$ 966,195