Shareholders' Equity - Narrative (Detail) - $ / shares						12 Months Ended
	Nov. 17, 2015	Aug. 24, 2015	May. 18, 2015	Jun. 30, 2014	May. 15, 2014	Dec. 31, 2015	Dec. 31, 2014	Nov. 30, 2013
Capital Unit [Line Items]
Preferred stock, par value (usd per share)						$ 1.00	$ 1.00
Preferred stock, liquidation preference (usd per share)						$ 25.00	$ 25.00
Stock dividend (percent)					10.00%
Stock dividend (shares)				2,429,375
Percent of outstanding shares authorized for repurchase								5.00%
Premium percent over current book value								20.00%
Warrants outstanding to purchase common stock (shares)						627,673	635,274
Minimum
Capital Unit [Line Items]
Purchase price of common stock (usd per share)						$ 9.55	$ 9.55
Maximum
Capital Unit [Line Items]
Purchase price of common stock (usd per share)						$ 73.01	$ 73.01
Series C Preferred Stock
Capital Unit [Line Items]
Preferred stock, shares issued			2,300,000
Preferred stock, par value (usd per share)			$ 1.00
Preferred stock, liquidation preference (usd per share)			$ 25.00
Preferred stock, fixed dividend rate						7.00%
Preferred stock, redemption price (usd per share)						$ 25.00
Preferred stock, dividends declared (usd per share)	$ 0.4375	$ 0.56875
Series C Preferred Stock | London Interbank Offered Rate (LIBOR)
Capital Unit [Line Items]
Preferred stock, floating dividend rate						5.30%