Fair Value Measurements (Details 3) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt and Capital Lease Obligations		$ 271,766	$ 198,857
Convertible Senior Notes Due March 2028 [Member] | Portion at Other than Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		238,497
Convertible Senior Notes Due March 2028 [Member] | Fair Value, Inputs, Level 1 [Member] | Portion at Other than Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		0
Convertible Senior Notes Due March 2028 [Member] | Fair Value, Inputs, Level 2 [Member] | Portion at Other than Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		238,497
Convertible Senior Notes Due March 2028 [Member] | Fair Value, Inputs, Level 3 [Member] | Portion at Other than Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt		0
Senior Notes due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt and Capital Lease Obligations	[1]	$ 0	175,991
Senior Notes due 2021 [Member] | Portion at Other than Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	[2]		184,373
Senior Notes due 2021 [Member] | Fair Value, Inputs, Level 1 [Member] | Portion at Other than Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	[2]		0
Senior Notes due 2021 [Member] | Fair Value, Inputs, Level 2 [Member] | Portion at Other than Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	[2]		184,373
Senior Notes due 2021 [Member] | Fair Value, Inputs, Level 3 [Member] | Portion at Other than Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of long-term debt	[2]		$ 0

[1] Net of unamortized debt issuance costs and premium received of $2.0 million at December 31, 2016.

[2] (1)Net of unamortized debt issuance costs and premium received of $2.0 million.