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Adoption of New Accounting Standards (Details) - USD ($) | 3 Months Ended
--- | ---
Mar. 31, 2017 | Mar. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |
Recognized a discrete tax benefit | $ 1,800,000 | $ 1,800,000
Reclassified tax benefits to operating activities | 81,520,530 | 75,541,699
Cash flows from operating activities | $ 131,191,171 | 151,868,528
Accounting Standards Update 2016-09 [Member] |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |
Reclassified tax benefits to operating activities |  | 400,000
Cash flows from operating activities |  | 400,000
Accounting Standards Update 2016-09 [Member] | Additional Paid-in Capital [Member] |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |
Tax benefit recognized as additional paid-in capital |  | (400,000)
Tax benefit recognized as additional paid-in capital, gross |  | 100,000
Tax benefit recognized as additional paid-in capital, tax |  | $ 500,000

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