CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Cumulative Earnings	Cumulative Distributions to Stockholders
Beginning balance (in shares) at Dec. 31, 2018		84,884,344
Balance at beginning of period at Dec. 31, 2018	$ 1,348,794	$ 849	$ 1,811,422	$ 61,297	$ 1,409,941	$ (1,934,715)
Increase (Decrease) in Stockholders' Equity
Net Income (Loss)	120,040				120,040
Other comprehensive income (loss)	(23,173)			(23,173)
Issuance of common stock (in shares)		26,666,191
Issuance of common stock	418,591	$ 267	418,324
Direct stock purchase and dividend reinvestment plan (in shares)		399,838
Direct stock purchase and dividend reinvestment plan	6,307	$ 4	6,303
Employee stock purchase and incentive plans (in shares)		151,358
Employee stock purchase and incentive plans	(1,766)	$ 1	(1,767)
Non-cash equity award compensation	10,552		10,552
Common dividends declared	(94,286)					(94,286)
Ending balance (in shares) at Sep. 30, 2019		112,101,731
Balance at End of Period at Sep. 30, 2019	1,785,059	$ 1,121	2,244,834	38,124	1,529,981	(2,029,001)
Beginning balance (in shares) at Jun. 30, 2019		97,715,021
Balance at beginning of period at Jun. 30, 2019	1,564,032	$ 977	2,013,044	48,923	1,495,671	(1,994,583)
Increase (Decrease) in Stockholders' Equity
Net Income (Loss)	34,310				34,310
Other comprehensive income (loss)	(10,799)			(10,799)
Issuance of common stock (in shares)		14,375,000
Issuance of common stock	228,483	$ 144	228,339
Employee stock purchase and incentive plans (in shares)		11,710
Employee stock purchase and incentive plans	154		154
Non-cash equity award compensation	3,297		3,297
Common dividends declared	(34,418)					(34,418)
Ending balance (in shares) at Sep. 30, 2019		112,101,731
Balance at End of Period at Sep. 30, 2019	1,785,059	$ 1,121	2,244,834	38,124	1,529,981	(2,029,001)
Beginning balance (in shares) at Dec. 31, 2019		114,353,036
Balance at beginning of period at Dec. 31, 2019	1,827,231	$ 1,144	2,269,617	41,513	1,579,124	(2,064,167)
Increase (Decrease) in Stockholders' Equity
Net Income (Loss)	(636,142)				(636,142)
Other comprehensive income (loss)	(62,073)			(62,073)
Issuance of common stock (in shares)		350,088
Issuance of common stock	5,547	$ 3	5,544
Direct stock purchase and dividend reinvestment plan (in shares)		0
Employee stock purchase and incentive plans (in shares)		248,533
Employee stock purchase and incentive plans	(2,765)	$ 2	(2,767)
Non-cash equity award compensation	11,146		11,146
Share repurchases (in shares)		(3,047,335)
Share repurchases	(21,659)	$ (30)	(21,629)
Common dividends declared	(67,821)					(67,821)
Ending balance (in shares) at Sep. 30, 2020		111,904,322
Balance at End of Period at Sep. 30, 2020	1,053,464	$ 1,119	2,261,911	(20,560)	942,982	(2,131,988)
Beginning balance (in shares) at Jun. 30, 2020		114,940,197
Balance at beginning of period at Jun. 30, 2020	936,576	$ 1,149	2,279,625	(29,391)	801,170	(2,115,977)
Increase (Decrease) in Stockholders' Equity
Net Income (Loss)	141,812				141,812
Other comprehensive income (loss)	8,831			8,831
Employee stock purchase and incentive plans (in shares)		11,460
Employee stock purchase and incentive plans	9	$ 0	9
Non-cash equity award compensation	3,906		3,906
Share repurchases (in shares)		(3,047,335)
Share repurchases	(21,659)	$ (30)	(21,629)
Common dividends declared	(16,011)					(16,011)
Ending balance (in shares) at Sep. 30, 2020		111,904,322
Balance at End of Period at Sep. 30, 2020	$ 1,053,464	$ 1,119	$ 2,261,911	$ (20,560)	$ 942,982	$ (2,131,988)