Derivatives (Interest rate swap agreements) (Details) - Swap Agreement Seventeen [Member] $ in Millions	3 Months Ended
	Jun. 30, 2019 USD ($)
Swaps:
Debt instrument, face amount	$ 0.0
Derivative, Inception Date	Jan. 11, 2013
Derivative Effective Date	Jan. 15, 2013
Derivative, Maturity Date	Dec. 15, 2019
Designated Cash Flow Hedge Date	Jan. 11, 2013