Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands								1 Months Ended			3 Months Ended		6 Months Ended		12 Months Ended
	Aug. 01, 2019	Jul. 26, 2019	Jul. 02, 2019	May 01, 2019	Apr. 24, 2019	Apr. 02, 2019	Feb. 22, 2019	Jun. 30, 2019	Jun. 30, 2018	May 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Common Shares
Common shares, shares issued								416,282,000			416,282,000		416,282,000		409,652,000
Proceeds from issuance of common shares, net of issuance costs														$ 302,014
Total aggregate amount of shares purchased								$ 80			$ 79		$ 79
Dividends to shareholders (in dollars per share)		$ 0.01			$ 0.01		$ 0.01				$ 0.01	$ 0.06	$ 0.02	$ 0.12
Cash dividends paid			$ 3,500			$ 3,500
Preferred shares, shares issued								5,746,000			5,746,000		5,746,000		5,750,000
Preferred stock, rate (as a percent)													6.00%		6.00%
Preferred stock, par value (in dollars per share)								$ 0.001			$ 0.001		$ 0.001		$ 0.001
Preferred stock, liquidation preference (in dollars per share)								$ 50			50		50		$ 50
Aggregate net proceeds														$ 278,573
Cash dividend per mandatory convertible preferred shares (in dollars per share)											$ 0.75	$ 0.64	$ 1.50
Mandatory Convertible Preferred Shares
Common Shares
Shares repurchased								4,000
Preferred shares, shares issued										5,750,000
Preferred stock, rate (as a percent)										6.00%
Preferred stock, par value (in dollars per share)										$ 0.001
Preferred stock, liquidation preference (in dollars per share)										$ 50
Cash dividend per mandatory convertible preferred shares (in dollars per share)		$ 0.75			$ 0.75		$ 0.75
Mandatory Convertible Preferred Shares | Underwriters option
Common Shares
Preferred shares, shares issued										750,000
Common Shares
Common Shares
Common shares, shares issued										35,000,000
Share price of shares purchased (in dollars per share)										$ 7.75
Proceeds from issuance of common shares, net of issuance costs									$ 301,400
Number of consecutive trading days to calculate average share price of common stock										20 days
Common Shares | Underwriters option
Common Shares
Common shares, shares issued									5,250,000			5,250,000		5,250,000
Common Shares | Minimum
Common Shares
Conversion ratio								5.6179		5.3763	5.6179		5.6179
Common Shares | Maximum
Common Shares
Conversion ratio								6.7416		6.4516	6.7416		6.7416
Common Shares | Mandatory Convertible Preferred Shares | Underwriters option
Common Shares
Aggregate net proceeds										$ 277,900
Retained Earnings | Mandatory Convertible Preferred Shares
Common Shares
Cash dividends paid	$ 4,300			$ 4,300