Organization and Business - Schedule of Basic and Diluted Earnings per Share (Parenthetical) (Detail) - shares	6 Months Ended	12 Months Ended
Jun. 30, 2013	Dec. 31, 2012
Diluted weighted average units outstanding, contingently issuable units		146,452
Class B Common Stock
Diluted weighted average units outstanding, contingently issuable units	228,549

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of contingently issuable shares. Contingently issuable shares are those shares that are issuable for little or no cash contingent on certain conditions being met.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 55
-URI http://asc.fasb.org/extlink&oid=7655603&loc=d3e2626-109256

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 48
-URI http://asc.fasb.org/extlink&oid=7655603&loc=d3e2538-109256

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Contingently Issuable Shares
-URI http://asc.fasb.org/extlink&oid=6508586

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Balance Type:	na
Period Type:	duration