Summary of Significant Accounting Policies - reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Reclassifications to financial statements
Other assets	$ 118,050		$ 118,050		$ 102,479
Other revenues	979	$ 1,390	2,169	$ 3,137
Other expense			100	$ 375
Deferred financing costs, net of amortization	$ 32,588		$ 32,588		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