Pre-Tax Book Income (Detail) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pre-tax Income [Line Items]
Income before income taxes	$ 46,973	$ 53,164	$ 88,319	$ 44,244	$ 60,676	$ 54,305	$ 141,483	$ 114,981	$ 188,456	$ 159,225	$ 223,177	$ 200,662	$ 182,472
Domestic
Pre-tax Income [Line Items]
Income before income taxes											148,296	149,988	178,451
Foreign
Pre-tax Income [Line Items]
Income before income taxes											$ 74,881	$ 50,674	$ 4,021