Dividends Paid - Additional Information (Detail) - $ / shares			6 Months Ended
	Jul. 21, 2015	Mar. 17, 2015	Jun. 30, 2015	Jun. 30, 2014
Dividends Payable [Line Items]
Dividends declared per common share			$ 0.43	$ 0.60
Dividend Declared
Dividends Payable [Line Items]
Dividends declared per common share		$ 0.10
Cash dividend, date dividend paid		May 15, 2015
Cash dividend, record date		May 01, 2015
Cash dividend, declaration date		Mar. 17, 2015
Dividend Declared | Subsequent Event
Dividends Payable [Line Items]
Dividends declared per common share	$ 0.10
Cash dividend, date dividend paid	Aug. 17, 2015
Cash dividend, record date	Aug. 03, 2015
Cash dividend, declaration date	Jul. 21, 2015