Derivative Instruments and Hedging Activities (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Unrealized gains, before tax	$ 9,800,000
Unrealized gains, net	7,300,000
Income recognized	120,000
Cash flow hedge gain (loss) to be reclassified	32,000,000
Cash flow hedge termination gain	3,000,000
Collateral requirements	157,800,000	$ 84,600,000
Variation margin, amount reducing derivative asset	193,400,000	113,700,000
Foreign Currency Exchange Forwards
Derivative [Line Items]
Notional amount	$ 47,200,000	$ 32,900,000