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		12 Months Ended	133 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Mar. 31, 2018	Nov. 30, 2016	Nov. 30, 2014	Oct. 31, 2011	Mar. 31, 2007
Capital Unit [Line Items]
Shares authorized for repurchase (in shares) (up to)					10,000,000	10,000,000		2,500,000
Shares authorized for additional repurchase (in shares)							5,000,000
Repurchase and retirement of common stock (in shares)	285,400			19,635,615
Repurchase and retirement of common stock	$ 1,729			$ 50,343
Shares repurchased, value	$ 932
Shares available for purchase (in shares)	7,864,385			7,864,385
Non-cash compensation expense	$ 1,494	$ 1,429
Shares surrendered for tax withholdings (in shares)	239,481
Preferred stock, shares authorized (in shares)	50,000,000		50,000,000	50,000,000
Common stock, shares authorized (in shares)	1,000,000,000		1,000,000,000	1,000,000,000
Series A Preferred Stock
Capital Unit [Line Items]
Preferred stock, shares authorized (in shares)	23,844,916		23,844,916	23,844,916
Dividends paid	$ 8,508
Dividends paid per share on monthly basis (in USD per share)	$ 0.1667
Common Stock
Capital Unit [Line Items]
Dividends paid	$ 1,960
Common stock cash dividend (in dollars per share)			$ 0.01
Employees
Capital Unit [Line Items]
Non-cash compensation expense	1,487
Options
Capital Unit [Line Items]
Unrecognized compensation cost for stock based compensation	$ 1,192			$ 1,192
Unrecognized compensation cost for stock based compensation, period of recognition	1 year 1 month 17 days
Purchase of shares (in shares)	684,669
Intrinsic value of options exercised	$ 1,021
Restricted shares
Capital Unit [Line Items]
Unrecognized compensation cost for stock based compensation	$ 10,631			10,631
Unrecognized compensation cost for stock based compensation, period of recognition	3 years
Restricted shares \| Employees
Capital Unit [Line Items]
Non-cash compensation expense	$ 1,487
Restricted shares \| Consultants and Independent Financial Advisors
Capital Unit [Line Items]
Non-cash compensation expense	7
Restricted shares \| Awards Granted in 2017
Capital Unit [Line Items]
Unrecognized compensation cost for stock based compensation	$ 5,597			$ 5,597
Unrecognized compensation cost for stock based compensation, period of recognition	3 years 8 months 50 days
Options, Warrants, and Other
Capital Unit [Line Items]
Shares surrendered for tax withholdings (in shares)	380,367