Employee Incentive Plan (Share-Based Compensation Units Issued) (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
Mar. 31, 2013 CELP Restricted Units [Member]	Jun. 30, 2013 Restricted Stock [Member]	Jun. 30, 2012 Restricted Stock [Member]	Jun. 30, 2013 Restricted Stock [Member]	Jun. 30, 2012 Restricted Stock [Member]	Jun. 30, 2013 Restricted Stock Units (RSUs) [Member]	Jun. 30, 2012 Restricted Stock Units (RSUs) [Member]	Jun. 30, 2013 Restricted Stock Units (RSUs) [Member]	Jun. 30, 2012 Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value of units vested		$ 298	$ 391	$ 4,303	$ 3,127	$ 279	$ 280	$ 4,293	$ 3,806
Fair value of units vested	$ 1,000	$ 217	$ 260	$ 2,184	$ 1,266	$ 222	$ 281	$ 2,496	$ 1,608

The total fair value of equity-based awards for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (d)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph c(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Period Type:	duration