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

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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=121583591&loc=d3e4304-108586

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Amount of paid and unpaid cash, stock, and paid-in-kind (PIK) dividends declared, for example, but not limited to, common and preferred stock.

+ 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
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6957935&loc=d3e64057-112817

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

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

+ References

No definition available.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Equity and dividends (Schedule of Quarterly Dividends Declared and Paid) (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Feb. 12, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Dividends Payable [Line Items]
Dividend per share	$ 0.22
Record date		Feb. 12, 2021
Payment date		Mar. 05, 2021
Fourth Quarter 2019 [Member]
Dividends Payable [Line Items]
Declaration date		Jan. 24, 2020
Dividend per share		$ 0.2000
Record date		Feb. 14, 2020
Total dividends		$ 21,905
Payment date		Mar. 06, 2020
First Quarter 2020 [Member]
Dividends Payable [Line Items]
Declaration date		May 06, 2020
Dividend per share		$ 0.2000
Record date		May 27, 2020
Total dividends		$ 21,681
Payment date		Jun. 17, 2020
Second Quarter 2020 [Member]
Dividends Payable [Line Items]
Declaration date		Aug. 05, 2020
Dividend per share		$ 0.2200
Record date		Aug. 26, 2020
Total dividends		$ 24,053
Payment date		Sep. 16, 2020
Third Quarter 2020 [Member]
Dividends Payable [Line Items]
Declaration date		Nov. 04, 2020
Dividend per share		$ 0.2200
Record date		Nov. 25, 2020
Total dividends		$ 24,098
Payment date		Dec. 16, 2020
Fourth Quarter 2018 [Member]
Dividends Payable [Line Items]
Declaration date			Jan. 25, 2019
Dividend per share			$ 0.1800
Record date			Feb. 15, 2019
Total dividends			$ 19,568
Payment date			Mar. 08, 2019
First Quarter 2019 [Member]
Dividends Payable [Line Items]
Declaration date			May 08, 2019
Dividend per share			$ 0.1800
Record date			May 29, 2019
Total dividends			$ 19,592
Payment date			Jun. 19, 2019
Second Quarter 2019 [Member]
Dividends Payable [Line Items]
Declaration date			Aug. 08, 2019
Dividend per share			$ 0.2000
Record date			Aug. 28, 2019
Total dividends			$ 21,631
Payment date			Sep. 18, 2019
Third Quarter 2019 [Member]
Dividends Payable [Line Items]
Declaration date			Nov. 07, 2019
Dividend per share			$ 0.2000
Record date			Nov. 27, 2019
Total dividends			$ 21,744
Payment date			Dec. 18, 2019
Fourth Quarter 2017 [Member]
Dividends Payable [Line Items]
Declaration date				Jan. 26, 2018
Dividend per share				$ 0.1700
Record date				Feb. 16, 2018
Total dividends				$ 18,246
Payment date				Mar. 09, 2018
First Quarter 2018 [Member]
Dividends Payable [Line Items]
Declaration date				May 09, 2018
Dividend per share				$ 0.1700
Record date				May 30, 2018
Total dividends				$ 18,342
Payment date				Jun. 20, 2018
Second Quarter 2018 [Member]
Dividends Payable [Line Items]
Declaration date				Aug. 07, 2018
Dividend per share				$ 0.1800
Record date				Aug. 29, 2018
Total dividends				$ 19,528
Payment date				Sep. 19, 2018
Third Quarter 2018 [Member]
Dividends Payable [Line Items]
Declaration date				Nov. 08, 2018
Dividend per share				$ 0.1800
Record date				Nov. 28, 2018
Total dividends				$ 19,562
Payment date				Dec. 19, 2018