Indebtedness (Details 1) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Senior Unsecured Notes Repurchases
Principal Amount Repurchased	$ 87,355
Purchase Price	89,328
2014 Notes [Member]
Senior Unsecured Notes Repurchases
Principal Amount Repurchased	9,000
Purchase Price	9,439
2028 Notes [Member]
Senior Unsecured Notes Repurchases
Principal Amount Repurchased	55,955
Purchase Price	57,041
2032 Notes [Member]
Senior Unsecured Notes Repurchases
Principal Amount Repurchased	22,400
Purchase Price	$ 22,848