Capital Stock, Dividends (Details) - USD ($)
$ / shares in Units, $ in Thousands |
3 Months Ended |
12 Months Ended |
Dec. 31, 2019 |
Sep. 30, 2019 |
Jun. 30, 2019 |
Mar. 31, 2019 |
Dec. 31, 2018 |
Sep. 30, 2018 |
Jun. 30, 2018 |
Mar. 31, 2018 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
| Dividends [Abstract] |
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| Payment of cash dividends |
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$ 82,189
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$ 80,581
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$ 76,058
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| Dividend Declared 2019-Q1 [Member] |
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| Dividends [Abstract] |
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| Cash dividend paid (in dollars per share) |
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$ 0.37
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| Dividend Declared 2019-Q2 [Member] |
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| Dividends [Abstract] |
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| Cash dividend paid (in dollars per share) |
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$ 0.37
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| Dividend Declared 2019-Q3 [Member] |
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| Dividends [Abstract] |
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| Cash dividend paid (in dollars per share) |
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$ 0.37
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| Dividend Declared 2019-Q4 [Member] |
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| Dividends [Abstract] |
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| Cash dividend paid (in dollars per share) |
$ 0.37
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| Dividend Declared 2018-Q1 [Member] |
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| Dividends [Abstract] |
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| Cash dividend paid (in dollars per share) |
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$ 0.365
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| Dividend Declared 2018-Q2 [Member] |
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| Dividends [Abstract] |
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| Cash dividend paid (in dollars per share) |
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$ 0.365
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| Dividend Declared 2018-Q3 [Member] |
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| Dividends [Abstract] |
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| Cash dividend paid (in dollars per share) |
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$ 0.365
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| Dividend Declared 2018-Q4 [Member] |
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| Dividends [Abstract] |
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| Cash dividend paid (in dollars per share) |
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$ 0.365
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| Dividend Declared 2020-Q1 [Member] |
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| Dividends [Abstract] |
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| Dividend payable per share (in dollars per share) |
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$ 0.375
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| Dividend payable, date to be paid |
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Mar. 11, 2020
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| Dividend payable, date of record |
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Feb. 28, 2020
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