Secured Financing Agreements - Principal Repayments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Repayment of secured financings
Total	$ 2,073,229		$ 2,073,229		$ 2,053,229
Secured financing agreements
Repayment of secured financings
2017 (remainder of)	910,569		910,569
2018	962,359		962,359
2019	408,015		408,015
2020	924,737		924,737
2021	451,040		451,040
Thereafter	1,132,276		1,132,276
Total	4,788,996		4,788,996		$ 4,197,218
Amortization of deferred financing costs from secured financing agreements included in interest expense	4,700	$ 4,300	9,400	$ 8,200
Repurchase Agreements
Repayment of secured financings
2017 (remainder of)	876,451		876,451
2018	894,295		894,295
2019	402,900		402,900
2020	578,062		578,062
2021	135,353		135,353
Thereafter	154,762		154,762
Total	3,041,823		3,041,823
Other Secured Financing
Repayment of secured financings
2017 (remainder of)	34,118		34,118
2018	68,064		68,064
2019	5,115		5,115
2020	346,675		346,675
2021	315,687		315,687
Thereafter	977,514		977,514
Total	$ 1,747,173		$ 1,747,173