Preferred Stock - Additional Information (Detail) (USD $)	3 Months Ended	0 Months Ended
	Mar. 31, 2015	Jan. 26, 2015	Oct. 27, 2014	Jul. 29, 2014	Apr. 30, 2014	Apr. 27, 2015	Apr. 29, 2014	Dec. 31, 2014
Class of Stock [Line Items]
Amount Of Non Voting Series A Preferred Stock Purchase price	$ 18,000,000
Non-voting Series A Preferred Stock, number of shares issued		1,800	1,800	1,800
Non-voting Series A Preferred Stock, maximum aggregate consideration							180,000,000
Redemption of preferred stock at purchase price	$ 10,000
Maximum [Member]
Class of Stock [Line Items]
Non-voting Series A Preferred Stock, number of shares issued							18,000
Non-Voting Series A Preferred Stock [Member]
Class of Stock [Line Items]
Issuance of non-voting Series A Preferred Stock, shares issued					9,000
Additional shares issued		1,800	1,800	1,800
Non-voting Series A Preferred Stock, shares purchased price					90,000,000
Amount Of Non Voting Series A Preferred Stock Purchase price		18,000,000	18,000,000	18,000,000
Non-voting Series A Preferred Stock, cumulative, non-participating cash dividend					0.10%
Subsequent Event [Member]
Class of Stock [Line Items]
Non-voting Series A Preferred Stock, number of shares issued						1,800
Subsequent Event [Member] | Non-Voting Series A Preferred Stock [Member]
Class of Stock [Line Items]
Additional shares issued						1,800
Amount Of Non Voting Series A Preferred Stock Purchase price						18,000,000
Preferred Stock [Member]
Class of Stock [Line Items]
Estimated fair value of derivatives	$ 3,000,000							$ 3,000,000