Equity - Reincorporation, Common Stock (Details)	1 Months Ended					12 Months Ended
	Feb. 28, 2019 $ / shares	Feb. 28, 2018 $ / shares	Feb. 28, 2017 $ / shares	Jul. 31, 2016 $ / shares	Feb. 28, 2015 $ / shares	Dec. 31, 2018 item $ / shares	Dec. 31, 2017 $ / shares	Dec. 31, 2016 $ / shares
Common Stock
Preferred stock, par value (in dollars per share)						$ 0.001	$ 0.001
Common stock, par value (in dollars per share)						$ 0.001	0.001
The number of consecutive years the company has paid regular common stock quarterly dividends. | item						59
Votes per share of common stock | item						1
Common stock quarterly dividend per share (in dollars per share)	$ 0.55	$ 0.50	$ 0.45	$ 0.425	$ 0.40	$ 2.00	$ 1.80	$ 1.65