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Fair Value Measurement - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended	0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Jan. 05, 2015
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Preferred stock liquidation preference per share	$ 10.00
Preferred stock dividend rate	3.00%
Common stock, par value	$ 0.00001		$ 0.00001
Net income (loss)	$ 5,501,000us-gaap_NetIncomeLoss	$ (3,380,000)us-gaap_NetIncomeLoss	$ 3,070,000us-gaap_NetIncomeLoss
Minimum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Percentage of closing stock price	10.00%
Estimated net income	37,200,000
Maximum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Percentage of closing stock price	10.00%
Estimated net income	37,100,000
Initial Conversion Price
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Common stock, par value	$ 2.25
Floor Price
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Common stock, par value	$ 1.75
Volatility Assumption [Member] \| Minimum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Percentage of closing stock price	10.00%
Estimated net income	11,300,000
Volatility Assumption [Member] \| Maximum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Percentage of closing stock price	10.00%
Estimated net income	11,500,000
Transaction Occurring Assumption [Member] \| Minimum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Percentage of closing stock price	10.00%
Estimated net income	6,600,000
Transaction Occurring Assumption [Member] \| Maximum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Percentage of closing stock price	10.00%
Estimated net income	6,600,000
Series B Preferred Stock [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Capital				$ 600,000,000
Convertible preferred stock, shares issued	600,000		0	600,000
Preferred stock liquidation preference per share				$ 1,000
Preferred stock dividend rate				3.00%
Common stock, par value	$ 1.75
Series B Preferred Stock [Member] \| Maximum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Common stock, par value	$ 2.25