Capital Structure and Accumulated Comprehensive Income (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 22, 2016	Mar. 31, 2015
Capital Structure And Accumulated Comprehensive Income (Loss)
SecondaryOfferingShares		10,000,000
Dividends Payable, Date Declared	Feb. 22, 2016
Issuance of common stock	$ 186,202,000
Common stock issued (shares)	64,007,899		53,374,963
Common stock outstanding (shares)	63,481,699		53,374,963
Preferred stock issued (shares)	0		0
Preferred stock outstanding (shares)	0		0
Authorization to repurchase common stock	$ 50,000,000
Repurchase of common stock (shares)	706,093
Average price per common share of repurchase common stock (in USD per share)	$ 23.83
Remaining authorized repurchase of common stock amount	$ 33,200,000
Common Stock
Capital Structure And Accumulated Comprehensive Income (Loss)
Common stock authorized (shares)	500,000,000
Common stock, par value	$ 0.01
Preferred Stock
Capital Structure And Accumulated Comprehensive Income (Loss)
Preferred stock authorized (shares)	10,000,000
Preferred stock, par value	$ 0.01