Earnings Per Share - Shares Repurchased (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Shares Repurchased [Line Items]
Total Number of Shares Repurchased	860	630	341
Total Cost of Shares Repurchased	$ 20,879	$ 12,581	$ 5,479
Minimum [Member]
Schedule Of Shares Repurchased [Line Items]
Range of Prices Paid Per Share	$ 22.81	$ 19.80	$ 15.61
Maximum [Member]
Schedule Of Shares Repurchased [Line Items]
Range of Prices Paid Per Share	$ 25.00	$ 20.00	$ 16.99