Derivatives (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2016		Sep. 30, 2015	Sep. 30, 2016		Sep. 30, 2015	Dec. 31, 2015
Derivative [Line Items]
Derivative assets, fair value		$ 12,985			$ 12,985			$ 7,835
Derivative assets, aggregate notional amount		425,000			425,000			460,000
Derivative liabilities, fair value		(84,023)			(84,023)			(41,205)
Derivative liabilities, aggregate notional amount		7,655,000			7,655,000			9,220,000
Interest Rate Swap
Derivative [Line Items]
Derivative assets, fair value		12,985			12,985			7,835
Derivative assets, aggregate notional amount		425,000			425,000			460,000
Derivative liabilities, fair value		(41,385)			(41,385)			(12,108)
Derivative liabilities, aggregate notional amount		1,355,000			1,355,000			2,920,000
Eurodollar Future
Derivative [Line Items]
Derivative assets, fair value		0			0			0
Derivative assets, aggregate notional amount		0	[1]		0	[1]		0
Derivative liabilities, fair value		(42,638)			(42,638)			(29,097)
Derivative liabilities, aggregate notional amount	[1]	6,300,000			6,300,000			$ 6,300,000
Pay-fixed interest rate swap | Interest Rate Swap
Derivative [Line Items]
(Loss) gain on derivative instruments, net				$ (48,697)	(59,912)
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
(Loss) gain on derivative instruments, net		2,409		(52,749)	(62,153)		$ (60,982)
Not Designated as Hedging Instrument [Member] | Eurodollar Future
Derivative [Line Items]
(Loss) gain on derivative instruments, net		2,830		(11,027)	(13,542)		(24,942)
Not Designated as Hedging Instrument [Member] | Receive-fixed interest rate swap | Interest Rate Swap
Derivative [Line Items]
(Loss) gain on derivative instruments, net		(2,976)		$ 6,975	$ 11,301		9,757
Not Designated as Hedging Instrument [Member] | Pay-fixed interest rate swap | Interest Rate Swap
Derivative [Line Items]
(Loss) gain on derivative instruments, net		$ 2,555					$ (45,797)

[1] The Eurodollar futures aggregate notional amount represents the total notional of the 3-month contracts with expiration dates from 2017 to 2020. The maximum notional outstanding for any future 3-month period did not exceed $725,000 as of September 30, 2016 or as of December 31, 2015.