Fair Value - Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Financial assets not carried at fair value:
HTM securities	$ 520,342	$ 321,244
Financial liabilities not carried at fair value:
Convertible senior notes	1,334,424	1,323,795
Carrying Value
Financial assets not carried at fair value:
Loans held-for-investment and loans transferred as secured borrowings	5,786,720	6,059,652
HTM securities	520,342	321,244
European servicing rights	1,589	2,626
Financial liabilities not carried at fair value:
Secured financing agreements and secured borrowings on transferred loans	4,570,889	4,068,699
Convertible senior notes	1,334,424	1,323,795
Fair Value.
Financial assets not carried at fair value:
Loans held-for-investment and loans transferred as secured borrowings	5,813,816	6,125,881
HTM securities	505,648	315,255
European servicing rights	4,406	5,302
Financial liabilities not carried at fair value:
Secured financing agreements and secured borrowings on transferred loans	4,564,186	4,092,264
Convertible senior notes	$ 1,347,889	$ 1,331,979