Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair value assets and liabilities measured on recurring basis:
Marketable equity securities	$ 17,396	$ 17,053
Fair value on a recurring basis | Fair Value
Fair value assets and liabilities measured on recurring basis:
Marketable equity securities	17,396
Total fair value assets and liabilities measured on recurring basis	5,878
Fair value on a recurring basis | Fair Value | Interest-rate swap contracts
Fair value assets and liabilities measured on recurring basis:
Derivative liabilities	(12,903)
Fair value on a recurring basis | Fair Value | Warrants
Fair value assets and liabilities measured on recurring basis:
Derivative assets	1,385
Fair value on a recurring basis | Level 1
Fair value assets and liabilities measured on recurring basis:
Marketable equity securities	17,396
Total fair value assets and liabilities measured on recurring basis	17,396
Fair value on a recurring basis | Level 2
Fair value assets and liabilities measured on recurring basis:
Total fair value assets and liabilities measured on recurring basis	(12,903)
Fair value on a recurring basis | Level 2 | Interest-rate swap contracts
Fair value assets and liabilities measured on recurring basis:
Derivative liabilities	(12,903)
Fair value on a recurring basis | Level 3
Fair value assets and liabilities measured on recurring basis:
Total fair value assets and liabilities measured on recurring basis	1,385
Fair value on a recurring basis | Level 3 | Warrants
Fair value assets and liabilities measured on recurring basis:
Derivative assets	$ 1,385