Shareholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2014
Stockholders Equity Note Disclosure [Line Items]
Common Stock, Shares Authorized	426.0		426.0
Common Stock, Par or Stated Value Per Share	$ 0.01		$ 0.01
Dividends Payable, Amount Per Share	0.35		0.35
Common Stock, Dividends, Per Share, Cash Paid	$ 0.345	$ 0.33
Share repurchase (in shares)	0.0
ApprovedNotDeclaredlDividends			$ 1.38
Dividends payable	$ 62.9		$ 61.8
December 2014 Share Repurchase Program [Member]
Stockholders Equity Note Disclosure [Line Items]
Repurchase of shares of our common stock up to a maximum aggregate value				$ 1,000.0
Common stock authorized for repurchase, expiration date	Dec. 31, 2019
Share repurchase program remaining available amount	$ 800.0