Consolidated Statements of Changes in Shareholders' Equity (Parenthetical)	3 Months Ended			12 Months Ended
	Mar. 31, 2020 Dividend	Mar. 31, 2019 Dividend	Mar. 31, 2018 Dividend	Dec. 31, 2020 $ / shares	[1]	Dec. 31, 2019 $ / shares	[1]	Dec. 31, 2018 $ / shares
Statement of Stockholders' Equity [Abstract]
Dividends declared per common share (in USD per share) | $ / shares				$ 1.75		$ 1.71		$ 1.66
Number of dividends declared per quarter | Dividend	2	2	2

[1] * Two dividends were declared in each of the first quarters of 2020, 2019 and 2018.