Employee Incentive Plan (Share-Based Compensation Units Issued) (Details) (USD $) In Thousands, unless otherwise specified	0 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Mar. 04, 2013 CELP Restricted Units [Member]	Sep. 30, 2013 Restricted Stock [Member]	Sep. 30, 2012 Restricted Stock [Member]	Sep. 30, 2013 Restricted Stock [Member]	Sep. 30, 2012 Restricted Stock [Member]	Sep. 30, 2013 Restricted Stock Units (RSUs) [Member]	Sep. 30, 2012 Restricted Stock Units (RSUs) [Member]	Sep. 30, 2013 Restricted Stock Units (RSUs) [Member]	Sep. 30, 2012 Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value of units vested		$ 3,290	$ 537	$ 7,593	$ 3,963	$ 2,457	$ 448	$ 6,750	$ 4,031
Fair value of units vested	$ 1,000	$ 1,123	$ 448	$ 3,307	$ 1,714	$ 1,275	$ 452	$ 3,771	$ 2,060