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Stock Acquisition Rights, Stock Options and Warrants (Narrative) (Details) - USD ($)			3 Months Ended		9 Months Ended
	Jan. 01, 2020	Sep. 15, 2014	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Jul. 31, 2019	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of stock, price per share							$ 45.00
Subsidiary equity units for which investor has right to convert to common stock			500,000		500,000
Cumulative effect of change in accounting principle									$ 768,000
Accounting Standards Update 2018-07 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cumulative effect of change in accounting principle								$ 14,000
2014 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding			23,550		23,550
Shares authorized			3,805,223		3,805,223
Common stock authorized and reserved for issuance			801,273		801,273
Maximum [Member] \| 2014 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of increase in number of shares of common stock issued and outstanding					5.00%
Subsequent Event [Member] \| 2014 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional common stock authorized and reserved for future issuance	342,762
Percentage of increase in number of shares of common stock issued and outstanding	2.00%
Common Class B Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion ratio					one
Common Class A [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of units owned			100.00%		100.00%
PDV Spectrum Holding Company, LLC [Member] \| Common Class B Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from investment, shares		500,000
Sale of stock, price per share		$ 20.00
Stock issued during period value to purchase of assets		$ 10,000,000
Non-Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to non-vested share options granted			$ 2,000,000		$ 2,000,000
Weighted average Period for each stock option award granted					2 years
Performance Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding			179,945		179,945			179,945
Stock compensation expense				$ 700,000		$ 5,600,000
Options, Granted
Performance Stock Options [Member] \| Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense				1,100,000		2,100,000
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding			1,815,436		1,815,436			1,923,634
Stock compensation expense			$ 300,000		$ 1,300,000
Unrecognized compensation cost related to non-vested share options granted			2,800,000		$ 2,800,000
Options, Granted					0
Stock Option [Member] \| Accounting Standards Update 2018-07 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cumulative effect of change in accounting principle								$ 174,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense			1,100,000	700,000	$ 3,100,000	3,400,000
Unvested compensation expense			9,800,000		$ 9,800,000
Weighted average period of recognition of unrecognized compensation cost					2 years 11 months 12 days
Restricted Stock [Member] \| Restructuring Charges [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense						1,400,000
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense			0	$ 0	$ 0	$ 0
Unvested compensation expense			$ 3,000,000		$ 3,000,000
Performance Stock Units [Member] \| 2014 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued during period			11,307		11,307