Long-Term Debt - Convertible Debt (Details)			12 Months Ended
	Aug. 05, 2016 USD ($) $ / shares	Mar. 11, 2015 USD ($) $ / shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Convertible notes face amount			$ 171,600,000
Unamortized debt discount of notes			$ 4,119,419
4.50% Convertible Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Convertible notes face amount		$ 75,000,000		$ 75,000,000
Debt Instrument Maturity Year		2020	2020	2020
Debt instrument interest rate		4.50%	4.50%
Line of credit facility, maturity date		Mar. 15, 2020
Debt instrument conversion ratio	14.5253	14.5136
Convertible notes principal amount	$ 1,000	$ 1,000
Conversion price per share | $ / shares	$ 68.84	$ 68.90	$ 68.90
Unamortized debt discount of notes		$ 6,100,000	$ 4,100,000
Remaining amortization period (in years)			3 years 2 months 12 days
Cash Discount for issuance of the notes		2,600,000
Equity component of the convertible notes issued		3,500,000		$ 2,100,000
Net proceeds from issuance of notes		72,400,000
Payments of Debt Issuance Costs		2,600,000
Credit facility repayments		$ 47,500,000