Summary of Significant Accounting Policies - reclassifications (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Reclassifications to financial statements
Deferred financing costs, net of amortization	$ 45,732		$ 38,336
Accounting Standards Update 2015-03 | Secured financing agreements | Reclassification Adjustment
Reclassifications to financial statements
Deferred financing costs, net of amortization			38,300
Accounting Standards Update 2015-03 | Convertible Senior Notes | Reclassification Adjustment
Reclassifications to financial statements
Deferred financing costs, net of amortization			$ 1,400
Accounting Standards Update 2015-02
Reclassifications to financial statements
Cumulative-effect adjustment to equity upon adoption		$ 0