Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Comprehensive (loss) income:
Beginning Balance	$ 234,700	$ 202,531
Comprehensive Income
Net (loss) income	(207,056)	5,053
Total comprehensive (loss) income	(207,056)	5,053
Income tax expense associated with the exercise of non-qualified stock options	(304)
Equity-based compensation expense	1,813	1,631
Net issuance of stock upon exercise of stock options and under stock plans for employees and directors	731	705
Distribution to partnership interests	(240)	(195)
Ending Balance	29,644	209,725
Common Stock [Member]
Comprehensive (loss) income:
Shares, Beginning Balance	32,009,286	31,435,264
Beginning Balance	3,201	3,144
Comprehensive Income
Net (loss) income	0	0
Total comprehensive (loss) income	0	0
Income tax expense associated with the exercise of non-qualified stock options	0
Equity-based compensation expense	0	0
Net issuance of stock upon exercise of stock options and under stock plans for employees and directors, Shares	501,401	122,390
Net issuance of stock upon exercise of stock options and under stock plans for employees and directors	50	14
Distribution to partnership interests	0	0
Shares, Ending Balance	32,510,687	31,557,654
Ending Balance	3,251	3,158
Additional Paid-in Capital [Member]
Comprehensive (loss) income:
Beginning Balance	399,148	387,803
Comprehensive Income
Net (loss) income	0	0
Total comprehensive (loss) income	0	0
Income tax expense associated with the exercise of non-qualified stock options	(304)
Equity-based compensation expense	1,813	1,631
Net issuance of stock upon exercise of stock options and under stock plans for employees and directors	942	691
Distribution to partnership interests	0	0
Ending Balance	401,599	390,125
Retained Earnings / Accumulated (deficit) [Member]
Comprehensive (loss) income:
Beginning Balance	(151,335)	(178,131)
Comprehensive Income
Net (loss) income	(207,177)	4,840
Total comprehensive (loss) income	(207,177)	4,840
Income tax expense associated with the exercise of non-qualified stock options	0
Equity-based compensation expense	0	0
Net issuance of stock upon exercise of stock options and under stock plans for employees and directors	0	0
Distribution to partnership interests	0	0
Ending Balance	(358,512)	(173,291)
Treasury Stock [Member]
Comprehensive (loss) income:
Beginning Balance	(17,852)	(12,878)
Comprehensive Income
Net (loss) income	0	0
Total comprehensive (loss) income	0	0
Income tax expense associated with the exercise of non-qualified stock options	0
Equity-based compensation expense	0	0
Net issuance of stock upon exercise of stock options and under stock plans for employees and directors	(261)	0
Distribution to partnership interests	0	0
Ending Balance	(18,113)	(12,878)
Noncontrolling Interests [Member]
Comprehensive (loss) income:
Beginning Balance	1,538	2,593
Comprehensive Income
Net (loss) income	121	213
Total comprehensive (loss) income	121	213
Income tax expense associated with the exercise of non-qualified stock options	0
Equity-based compensation expense	0	0
Net issuance of stock upon exercise of stock options and under stock plans for employees and directors	0	0
Distribution to partnership interests	(240)	(195)
Ending Balance	$ 1,419	$ 2,611