Fair Value Measurements (Details) $ in Thousands	Mar. 31, 2016 USD ($) derivative	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Embedded derivative	$ (186,783)	$ (193,077)
Number of interest rate derivatives | derivative	0
Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Embedded derivative	$ (186,783)	(193,077)
Total net assets	(158,870)	(162,059)
Fair value of derivative instruments	27,913	31,018
Fair Value, Inputs, Level 2 [Member] | Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	27,913	31,018
Total net assets	27,913	31,018
Fair Value, Inputs, Level 3 [Member] | Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Embedded derivative	(186,783)	(193,077)
Total net assets	$ (186,783)	$ (193,077)