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Aggregate dividends paid during the period for each share of common stock outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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- Definition

Date the declared dividend will be paid, in CCYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

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- Definition

Date the dividend to be paid was declared, in CCYY-MM-DD format.

+ References

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- Definition

Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

+ References

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- Definition

Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

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Capital Stock and Changes in Capital Accounts, Cash Dividends Paid (Details) - USD ($) $ / shares in Units, $ in Thousands									12 Months Ended
	Apr. 17, 2019	Mar. 20, 2019	Jan. 16, 2019	Dec. 19, 2018	Oct. 24, 2018	Sep. 26, 2018	Jul. 18, 2018	Jun. 21, 2018	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Cash dividend [Abstract]
Cash dividends	$ 18,600		$ 18,900		$ 18,900		$ 19,000		$ 75,752	$ 73,542	$ 71,545
Class A Common Stock [Member]
Cash dividend [Abstract]
Common stock dividend (in dollars per share)									$ 1.32	$ 1.28	$ 1.24
Class A Common Stock [Member] \| Dividend Declared in Q1 2019 [Member]
Cash dividend [Abstract]
Dividend declared date									Jun. 21, 2018
Common stock dividend (in dollars per share)								$ 0.33
Dividend paid date									Jul. 18, 2018
Dividend record date									Jul. 03, 2018
Class A Common Stock [Member] \| Dividend Declared in Q2 2019 [Member]
Cash dividend [Abstract]
Dividend declared date									Sep. 26, 2018
Common stock dividend (in dollars per share)						$ 0.33
Dividend paid date									Oct. 24, 2018
Dividend record date									Oct. 09, 2018
Class A Common Stock [Member] \| Dividend Declared in Q3 2019 [Member]
Cash dividend [Abstract]
Dividend declared date									Dec. 19, 2018
Common stock dividend (in dollars per share)				$ 0.33
Dividend paid date									Jan. 16, 2019
Dividend record date									Jan. 02, 2019
Class A Common Stock [Member] \| Dividend Declared in Q4 2019 [Member]
Cash dividend [Abstract]
Dividend declared date									Mar. 20, 2019
Common stock dividend (in dollars per share)		$ 0.33
Dividend paid date									Apr. 17, 2019
Dividend record date									Apr. 02, 2019
Class B Common [Member]
Cash dividend [Abstract]
Common stock dividend (in dollars per share)									$ 1.32	$ 1.28	$ 1.24
Class B Common [Member] \| Dividend Declared in Q1 2019 [Member]
Cash dividend [Abstract]
Dividend declared date									Jun. 21, 2018
Common stock dividend (in dollars per share)								$ 0.33
Dividend paid date									Jul. 18, 2018
Dividend record date									Jul. 03, 2018
Class B Common [Member] \| Dividend Declared in Q2 2019 [Member]
Cash dividend [Abstract]
Dividend declared date									Sep. 26, 2018
Common stock dividend (in dollars per share)						$ 0.33
Dividend paid date									Oct. 24, 2018
Dividend record date									Oct. 09, 2018
Class B Common [Member] \| Dividend Declared in Q3 2019 [Member]
Cash dividend [Abstract]
Dividend declared date									Dec. 19, 2018
Common stock dividend (in dollars per share)				$ 0.33
Dividend paid date									Jan. 16, 2019
Dividend record date									Jan. 02, 2019
Class B Common [Member] \| Dividend Declared in Q4 2019 [Member]
Cash dividend [Abstract]
Dividend declared date									Mar. 20, 2019
Common stock dividend (in dollars per share)		$ 0.33
Dividend paid date									Apr. 17, 2019
Dividend record date									Apr. 02, 2019