Quarterly report pursuant to Section 13 or 15(d)

Shareholders' Equity - Narrative (Details)

Shareholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				9 Months Ended		139 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Nov. 30, 2016
Capital Unit [Line Items]
Shares authorized for repurchase (in shares) (up to)								27,500,000
Repurchase and retirement of common stock (in shares)	1,724,113				2,481,728		21,831,943
Repurchase and retirement of common stock					$ 8,746		$ 57,298
Shares repurchased, value	$ 5,318				$ 7,887
Shares available for purchase (in shares)	5,668,057				5,668,057		5,668,057
Non-cash compensation expense	$ 1,380			$ 1,341	$ 4,442	$ 4,148
Shares surrendered for tax withholdings (in shares)					247,379
Preferred stock dividends declared and paid	8,507				$ 25,523
Common stock dividends declared and paid	$ (2,448)				$ (6,377)
Series A Preferred Stock
Capital Unit [Line Items]
Dividends paid per share on monthly basis (in dollars per share)					$ 0.1667
Common Stock
Capital Unit [Line Items]
Common stock cash dividend (in dollars per share)	$ 0.0125	$ 0.01	$ 0.01
Employees
Capital Unit [Line Items]
Stock-based compensation					$ 4,408
Consultants and Independent Financial Advisors
Capital Unit [Line Items]
Stock-based compensation	$ 7				34
Options
Capital Unit [Line Items]
Unrecognized compensation cost for stock based compensation	$ 476				$ 476		$ 476
Unrecognized compensation cost for stock based compensation, period of recognition					9 months 50 days
Purchase of shares (in shares)	778,234				2,488,446
Intrinsic value of options exercised	$ 836				$ 3,771
Restricted shares
Capital Unit [Line Items]
Unrecognized compensation cost for stock based compensation	8,756				$ 8,756		8,756
Unrecognized compensation cost for stock based compensation, period of recognition					2 years 6 months 48 days
Restricted shares \| Employees
Capital Unit [Line Items]
Non-cash compensation expense	1,373				$ 4,408
Restricted shares \| Awards Granted In 2018
Capital Unit [Line Items]
Unrecognized compensation cost for stock based compensation	$ 5,330				$ 5,330		$ 5,330
Unrecognized compensation cost for stock based compensation, period of recognition					3 years 2 months 2 days
Options, Warrants, and Other
Capital Unit [Line Items]
Shares surrendered for tax withholdings (in shares)	0				469,805
Additional Paid-In Capital
Capital Unit [Line Items]
Repurchase and retirement of common stock					$ 8,746
Preferred stock dividends declared and paid					25,523
Common stock dividends declared and paid					(6,377)
Additional Paid-In Capital \| Employees
Capital Unit [Line Items]
Stock-based compensation					$ 4,408