Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Preferred Shares [Member]	Common Shares [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]
Balance, Amount at Dec. 31, 2017	$ 1,544,585	$ 299,707	$ 613	$ 1,290,931	$ (46,666)
Balance, Shares at Dec. 31, 2017		12,400	61,334
Balance, Shares (Accounting Standards Update 2014-11 Transfers and Servicing [Member]) at Dec. 31, 2017		12,400	61,334
Net income	64,611			0	64,611
Share-based compensation, Amount	2,756		$ 3	2,753	0
Share-based compensation, Shares			288
Dividends:
Common share dividends	(57,635)		$ 0	0	(57,635)
Preferred shares dividends	(12,472)	$ 0	0	0	(12,472)
Repurchase of common shares, Amount	$ (10,719)		$ (6)	(10,713)	0
Repurchase of common shares, Shares	(671)		(671)
Balance, Amount at Jun. 30, 2018	$ 1,545,487	$ 299,707	$ 610	1,282,971	(37,801)
Balance, Shares at Jun. 30, 2018		12,400	60,951
Balance, Amount (Accounting Standards Update 2014-11 Transfers and Servicing [Member]) at Dec. 31, 2017	14,361	$ 0	$ 0	0	14,361
Balance, Amount (Accounting Standards Update 2014-11 Transfers and Servicing [Member]) at Dec. 31, 2017	1,558,946	299,707	613	1,290,931	(32,305)
Balance, Amount at Mar. 31, 2018	1,542,258	$ 299,707	$ 609	1,281,115	(39,173)
Balance, Shares at Mar. 31, 2018		12,400	60,883
Net income	36,425			0	36,425
Share-based compensation, Amount	1,857		$ 1	1,856	0
Share-based compensation, Shares			68
Dividends:
Common share dividends	(28,817)	$ 0	$ 0	0	(28,817)
Preferred shares dividends	(6,236)	0	0	0	(6,236)
Balance, Amount at Jun. 30, 2018	1,545,487	$ 299,707	$ 610	1,282,971	(37,801)
Balance, Shares at Jun. 30, 2018		12,400	60,951
Balance, Amount at Dec. 31, 2018	1,566,132	$ 299,707	$ 610	1,285,533	(19,718)
Balance, Shares at Dec. 31, 2018		12,400	60,951
Balance, Amount at Mar. 31, 2019	1,727,589	$ 299,707	$ 684	1,431,887	(4,689)
Balance, Shares at Mar. 31, 2019		12,400	68,412
Balance, Amount at Dec. 31, 2018	1,566,132	$ 299,707	$ 610	1,285,533	(19,718)
Balance, Shares at Dec. 31, 2018		12,400	60,951
Net income	97,760			0	97,760
Share-based compensation, Amount	432		$ 2	430	0
Share-based compensation, Shares			240
Issuance of common shares, Amount	366,188	$ 0	$ 174	366,014	0
Issuance of common shares, Shares			17,416
Issuance costs relating to common shares	(4,791)	0	$ 0	(4,791)	0
Dividends:
Common share dividends	(69,315)	0	0	0	(69,315)
Preferred shares dividends	(12,472)			0	(12,472)
Balance, Amount at Jun. 30, 2019	1,943,934	$ 299,707	$ 786	1,647,186	(3,745)
Balance, Shares at Jun. 30, 2019		12,400	78,607
Balance, Amount at Mar. 31, 2019	1,727,589	$ 299,707	$ 684	1,431,887	(4,689)
Balance, Shares at Mar. 31, 2019		12,400	68,412
Net income	44,233			0	44,233
Share-based compensation, Amount	1,415		$ 0	1,415	0
Issuance of common shares, Amount	216,721	$ 0	$ 102	216,619	0
Issuance of common shares, Shares			10,195
Issuance costs relating to common shares	(2,735)	0	$ 0	(2,735)	0
Dividends:
Common share dividends	(37,053)	0	0	0	(37,053)
Preferred shares dividends	(6,236)	0	0	0	(6,236)
Balance, Amount at Jun. 30, 2019	$ 1,943,934	$ 299,707	$ 786	$ 1,647,186	$ (3,745)
Balance, Shares at Jun. 30, 2019		12,400	78,607