Valuation and Qualifying Accounts - Summary of Valuation and Qualifying Accounts (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 18,994,804	$ 12,946,077	$ 15,951,497
Charged / credited to Net income / (loss)	20,863,867	19,093,704	17,280,243
Charges Utilized / Write-offs	(23,693,230)	(13,044,977)	(20,285,663)
Balance at end of year	16,165,441	18,994,804	12,946,077
Credit Cards Receivable Allowance for Chargebacks [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	1,009,071	160,458	205,107
Charged / credited to Net income / (loss)	668,834	877,312	414,145
Charges Utilized / Write-offs	(1,148,677)	(28,699)	(458,794)
Balance at end of year	529,228	1,009,071	160,458
Tax Valuation Allowance [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	3,089,113	3,226,177	2,885,596
Charged / credited to Net income / (loss)	1,608,264	398,223	837,473
Charges Utilized / Write-offs	(166,145)	(535,287)	(496,892)
Balance at end of year	4,531,232	3,089,113	3,226,177
Contingencies [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	3,330,108	2,800,197	1,765,242
Charged / credited to Net income / (loss)	3,650,230	3,358,538	2,700,988
Charges Utilized / Write-offs	(3,971,801)	(2,828,627)	(1,666,033)
Balance at end of year	$ 3,008,537	$ 3,330,108	$ 2,800,197

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 09

-Article 12

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