Earnings Per Share - Shares Repurchased (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended		112 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020
Schedule Of Shares Repurchased [Line Items]
Total Cost of Shares Repurchased	$ 52,176	$ 30,281
Minimum [Member]
Schedule Of Shares Repurchased [Line Items]
Range of Prices Paid Per Share	$ 23.33	$ 24.72
Maximum [Member]
Schedule Of Shares Repurchased [Line Items]
Range of Prices Paid Per Share	$ 33.21	$ 28.00
2011 Share Repurchase Program [Member]
Schedule Of Shares Repurchased [Line Items]
Total Number of Shares Repurchased	1,860	1,140	8,300