Stockholders' Equity - Summary of Quarterly Share Repurchases (Detail) - $ / shares	3 Months Ended			12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Number of common stock shares repurchased	88,700	95,800	90,226	0	274,726	23,900
Maximum [Member]
Class of Stock [Line Items]
Repurchased shares, price per share	$ 43.95	$ 44.48	$ 39.99		$ 44.48
Minimum [Member]
Class of Stock [Line Items]
Repurchased shares, price per share	$ 42.72	$ 39.04	$ 38.06		$ 38.06