STOCKHOLDERS' EQUITY - Exchange offer with respect to Series A through E preferred stock (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Class Of Stock [Line Items]
Liquidation value per share	$ 25
Preferred stock, shares outstanding	1,444,146	2,521,872
Preferred Stock Value	$ 36,104	$ 63,047
Exchange Of Preferred Stock Series For Common Stock [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	2,521,872
Shares of preferred stock exchanged	1,077,726
Preferred Stock Shares Outstanding After Exchange	1,444,146
Preferred Stock Value	36,104
Shares of common stock issued	4,597,121
7.125% Noncumulative Perpetual Monthly Income Preferred Stock, Series A [Member]
Class Of Stock [Line Items]
Preferred stock dividend rate percentage	7.125%
7.125% Noncumulative Perpetual Monthly Income Preferred Stock, Series A [Member] | Exchange Of Preferred Stock Series For Common Stock [Member]
Class Of Stock [Line Items]
Liquidation value per share	$ 25
Preferred stock, shares outstanding	450,195
Shares of preferred stock exchanged	252,809
Preferred Stock Shares Outstanding After Exchange	197,386
Preferred Stock Value	4,935
Shares of common stock issued	1,081,652
Preferred stock dividend rate percentage	7.125%
8.35% Noncumulative Perpetual Monthly Income Preferred Stock, Series B [Member]
Class Of Stock [Line Items]
Preferred stock dividend rate percentage	8.35%
8.35% Noncumulative Perpetual Monthly Income Preferred Stock, Series B [Member] | Exchange Of Preferred Stock Series For Common Stock [Member]
Class Of Stock [Line Items]
Liquidation value per share	$ 25
Preferred stock, shares outstanding	475,987
Shares of preferred stock exchanged	179,841
Preferred Stock Shares Outstanding After Exchange	296,146
Preferred Stock Value	7,404
Shares of common stock issued	769,379
Preferred stock dividend rate percentage	8.35%
7.40% Noncumulative Perpetual Monthly Income Preferred Stock, Series C [Member]
Class Of Stock [Line Items]
Preferred stock dividend rate percentage	7.40%
7.40% Noncumulative Perpetual Monthly Income Preferred Stock, Series C [Member] | Exchange Of Preferred Stock Series For Common Stock [Member]
Class Of Stock [Line Items]
Liquidation value per share	$ 25
Preferred stock, shares outstanding	460,611
Shares of preferred stock exchanged	210,759
Preferred Stock Shares Outstanding After Exchange	249,852
Preferred Stock Value	6,246
Shares of common stock issued	890,830
Preferred stock dividend rate percentage	7.40%
7.25% Noncumulative Perpetual Monthly Income Preferred Stock, Series D [Member]
Class Of Stock [Line Items]
Preferred stock dividend rate percentage	7.25%
7.25% Noncumulative Perpetual Monthly Income Preferred Stock, Series D [Member] | Exchange Of Preferred Stock Series For Common Stock [Member]
Class Of Stock [Line Items]
Liquidation value per share	$ 25
Preferred stock, shares outstanding	510,592
Shares of preferred stock exchanged	225,070
Preferred Stock Shares Outstanding After Exchange	285,522
Preferred Stock Value	7,138
Shares of common stock issued	961,724
Preferred stock dividend rate percentage	7.25%
7.00% Noncumulative Perpetual Monthly Income Preferred Stock, Series E [Member]
Class Of Stock [Line Items]
Preferred stock dividend rate percentage	7.00%
7.00% Noncumulative Perpetual Monthly Income Preferred Stock, Series E [Member] | Exchange Of Preferred Stock Series For Common Stock [Member]
Class Of Stock [Line Items]
Liquidation value per share	$ 25
Preferred stock, shares outstanding	624,487
Shares of preferred stock exchanged	209,247
Preferred Stock Shares Outstanding After Exchange	415,240
Preferred Stock Value	$ 10,381
Shares of common stock issued	893,536
Preferred stock dividend rate percentage	7.00%