Fair Value Measurements (Summary of Fair Value of Freestanding Derivative) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Mar. 31, 2019
Not Designated as Hedging Instrument [Member] \| Dividend Receivable [Member]
Derivatives Fair Value [Line Items]
Fair Values of Derivative Financial Instruments Asset (Liability)	$ 34,547	$ 81,264

Fair value of the assets less the liabilities of a derivative or group of derivatives.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

Name:	us-gaap_DerivativeFairValueOfDerivativeNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant