Subsequent Event - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions				6 Months Ended
	Jul. 27, 2015	Jul. 03, 2015	Jul. 02, 2015	Jun. 30, 2015
Subsequent Event [Line Items]
Partnership exchangeable unit				$ 0.19
Subsequent Event [Member]
Subsequent Event [Line Items]
Cash dividend paid per common share		$ 0.10
Cash dividend paid per preferred share			$ 0.98
Dividend payable record date	Aug. 28, 2015	May 29, 2015
Dividends Payable preferred share			$ 67.5
Cash dividend declared by board	$ 0.12
Dividend to be paid date	Oct. 02, 2015
Subsequent Event [Member] | Preferred Class A [Member]
Subsequent Event [Line Items]
Dividend payable record date	Oct. 01, 2015
Dividends Payable preferred share	$ 67.5
Cash dividend declared by board	$ 0.98
Subsequent Event [Member] | Class B Exchangeable Limited Partnership Units [Member]
Subsequent Event [Line Items]
Partnership exchangeable unit	$ 0.12	$ 0.10