CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative Effect, Period Of Adoption, Adjustment	[1]	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period Of Adoption, Adjustment	[1]	Treasury Stock	Accumulated Other Comprehensive Income
Beginning balance - Shares at Dec. 31, 2018				(6,000,000)	(50,201,127)					(417)
Beginning balance - Amount at Dec. 31, 2018	$ 2,480,308			$ 150,000	$ 502	$ 967,890	$ 1,361,406			$ (8)	$ 518
Comprehensive income:
Net income	247,595						247,595
Change in unrealized gain (loss) on available-for-sale securities, net of taxes	8,493										8,493
Comprehensive income	256,088
Stock-based compensation expense recognized in earnings	8,565					8,565
Preferred stock dividend	(7,313)						(7,313)
Issuance of stock related to stock-based awards - Shares					108,176
Issuance of stock related to stock-based awards - Amount	(1,655)				$ 1	(1,656)
Issuance of common stock related to warrants - shares					8,768
Issuance of common stock related to warrants	0
Ending balance - Amount at Sep. 30, 2019	2,735,993			$ 150,000	$ 503	974,799	1,601,688			$ (8)	9,011
Ending balance - Shares at Sep. 30, 2019				(6,000,000)	(50,318,071)					(417)
Beginning balance - Shares at Jun. 30, 2019				(6,000,000)	(50,297,969)					(417)
Beginning balance - Amount at Jun. 30, 2019	2,647,071			$ 150,000	$ 503	972,219	1,516,044			$ (8)	8,313
Comprehensive income:
Net income	88,082						88,082
Change in unrealized gain (loss) on available-for-sale securities, net of taxes	698										698
Comprehensive income	88,780
Stock-based compensation expense recognized in earnings	3,023					3,023
Preferred stock dividend	(2,438)						(2,438)
Issuance of stock related to stock-based awards - Shares					20,102
Issuance of stock related to stock-based awards - Amount	(443)					(443)
Ending balance - Amount at Sep. 30, 2019	2,735,993			$ 150,000	$ 503	974,799	1,601,688			$ (8)	9,011
Ending balance - Shares at Sep. 30, 2019				(6,000,000)	(50,318,071)					(417)
Beginning balance - Shares at Dec. 31, 2019				(6,000,000)	(50,338,158)					(417)
Beginning balance - Amount at Dec. 31, 2019	2,801,321	$ (7,154)		$ 150,000	$ 503	978,205	1,663,671	$ (7,154)		$ (8)	8,950
Comprehensive income:
Net income	6,113						6,113
Change in unrealized gain (loss) on available-for-sale securities, net of taxes	(2,113)										(2,113)
Comprehensive income	4,000
Stock-based compensation expense recognized in earnings	11,348					11,348
Preferred stock dividend	(7,313)						(7,313)
Issuance of stock related to stock-based awards - Shares					117,811
Issuance of stock related to stock-based awards - Amount	(1,798)				$ 1	(1,799)
Ending balance - Amount at Sep. 30, 2020	2,800,404			$ 150,000	$ 504	987,754	1,655,317			$ (8)	6,837
Ending balance - Shares at Sep. 30, 2020				(6,000,000)	(50,455,969)					(417)
Beginning balance - Shares at Jun. 30, 2020				(6,000,000)	(50,436,089)					(417)
Beginning balance - Amount at Jun. 30, 2020	2,734,755			$ 150,000	$ 504	983,144	1,600,639			$ (8)	476
Comprehensive income:
Net income	57,116						57,116
Change in unrealized gain (loss) on available-for-sale securities, net of taxes	6,361										6,361
Comprehensive income	63,477
Stock-based compensation expense recognized in earnings	4,799					4,799
Preferred stock dividend	(2,438)						(2,438)
Issuance of stock related to stock-based awards - Shares					19,880
Issuance of stock related to stock-based awards - Amount	(189)					(189)
Ending balance - Amount at Sep. 30, 2020	$ 2,800,404			$ 150,000	$ 504	$ 987,754	$ 1,655,317			$ (8)	$ 6,837
Ending balance - Shares at Sep. 30, 2020				(6,000,000)	(50,455,969)					(417)

[1] Represents the impact of adopting Accounting Standard Update ("ASU") 2016-13. See Note 1 to the consolidated financial statements for more information.