Equity, Other Comprehensive Income, and Accumulated Other Comprehensive Income - Detailed Activities of Equity and Redeemable Noncontrolling Interest (Parenthetical) (Detail) - $ / shares	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Stockholders' Equity [Abstract]
Dividends declared Common, per share	$ 0.405	$ 0.365	$ 1.215	$ 1.095	$ 1.580	$ 1.425