Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity Schedule of Accumulated Other Comprehensive Income (Loss) (Details)

v3.8.0.1
Stockholders' Equity Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]    
Accumulated other comprehensive income $ 334,813 $ 199,227
Collateralized Mortgage Backed Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Unrealized gains 475,694 393,555
Unrealized losses $ (140,881) $ (194,328)