Earnings (Loss) Per Share - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 28, 2013		Jun. 29, 2013		Mar. 30, 2013		Dec. 31, 2012		Sep. 29, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Computation Of Earnings Per Share Line Items
Net income (loss) attributable to Pentair Ltd.	$ 158.2		$ 172.8		$ 154.1		$ 51.7		$ (273.1)		$ 31.4		$ 72.8		$ 61.7		$ 536.8		$ (107.2)		$ (7.5)
Weighted average common shares outstanding
Basic (shares)																	201.1		127.4		98.2
Dilutive impact of stock options and restricted stock awards (shares)																	3.5		0		0
Diluted (shares)																	204.6		127.4		98.2
Earnings (loss) per common share attributable to Pentair Ltd.
Basic earnings (loss) per common share (USD per share)	$ 0.80	[1]	$ 0.87	[1]	$ 0.76	[1]	$ 0.25	[1]	$ (1.31)	[1]	$ 0.31	[1]	$ 0.73	[1]	$ 0.63	[1]	$ 2.67	[1]	$ (0.84)	[1]	$ (0.08)
Diluted earnings (loss) per common share (USD per share)	$ 0.78	[1]	$ 0.85	[1]	$ 0.75	[1]	$ 0.25	[1]	$ (1.31)	[1]	$ 0.31	[1]	$ 0.72	[1]	$ 0.62	[1]	$ 2.62	[1]	$ (0.84)	[1]	$ (0.08)
Anti-dilutive stock options excluded from the calculation of diluted earnings per share																	0.2		16.0		8.4

[1] Amounts may not total to annual earnings because each quarter and year are calculated separately based on basic and diluted weighted-average common shares outstanding during that period