Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Derivative assets (Narrative) (Details)

v3.8.0.1
Derivative assets (Narrative) (Details) - USD ($)
Dec. 31, 2017
Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]    
Derivative cash collateral, obligation to return cash $ 3,700,000 $ 8,600,000
Derivative cash collateral, advanced to counterparties $ 0 $ 0