Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		6 Months Ended
	Jul. 12, 2016	Jun. 30, 2016	Jul. 11, 2016	Dec. 31, 2015	[1]
Subsequent Event [Line Items]
Common Stock, shares issued		924,929,607		935,929,561
Dividend record date		Jul. 11, 2016
Subsequent Event | 7.625% Series E Cumulative Redeemable Preferred Stock
Subsequent Event [Line Items]
Preferred Stock, par value	$ 0.01
Hatteras
Subsequent Event [Line Items]
Consulting fees		$ 0.7
Consulting agreement period		30 months
Transaction costs		$ 2.2
Hatteras | Subsequent Event
Subsequent Event [Line Items]
Business combination consideration transferred	$ 1,500.0
Common Stock, shares issued	93,900,000
Controlling financial interest obtained			74.12%
Hatteras | Subsequent Event | Atlantic Capital Advisors LLC
Subsequent Event [Line Items]
Termination Fee payable to ACA	$ 45.4
Hatteras | Subsequent Event | 7.625% Series A Cumulative Redeemable Preferred Stock
Subsequent Event [Line Items]
Preferred Stock, par value	$ 0.001

[1] Derived from the audited consolidated financial statements at December 31, 2015.