This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity, not expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities and unrealized holding gain (loss) related to transfers of securities into the available-for-sale classification and out of the held-to-maturity classification.

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Amount after tax and reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

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Amount after tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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The cash outflow associated with the purchase of all investments (debt, security, other) during the period.

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Investments - Additional Information (Detail) (USD $)	12 Months Ended
Investments - Additional Information (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Held-to-maturity Securities [Line Items]
Investment income	$ 6,312,498us-gaap_InvestmentIncomeInterest	$ 3,302,545us-gaap_InvestmentIncomeInterest	$ 2,451,731us-gaap_InvestmentIncomeInterest
Held-to-maturity investments, long-term	5,157,464	10,480,964
Other comprehensive income-change in fair value of available-for-sale investments	832,372
Other comprehensive income-realized gains reclassified from other comprehensive income to "investment income"	410,048
Other comprehensive income-net unrealized gains on the available-for-sale investments	422,324
Amortized cost of the available-for-sale investments	14,324,227
Held-to-maturity investments
Schedule of Held-to-maturity Securities [Line Items]
Investment income	2,027,454	2,510,647	3,044,856
Interest receivable	862,001	856,068	539,586
Held-to-maturity investments \| Debt Securities of Certain Real Estate Funds
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities		7,100,203	11,917,947
Held-to-maturity securities, 2016
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity investments, long-term	2,095,220
Held-to-maturity securities, 2017
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity investments, long-term	1,450,536
Held-to-maturity securities, 2019
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity investments, long-term	1,611,708
Trading Securities
Schedule of Held-to-maturity Securities [Line Items]
Investment income	1,390,200	1,413,810
PPDAI Group Inc. \| Series B Preferred Stock
Schedule of Held-to-maturity Securities [Line Items]
Payment to acquire investment	$ 2,224,999
Percentage of investee's issued share capital	2.62%