Acquisitions (Summary of the Consideration Transferred and the Fair Values of the Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands		6 Months Ended
		Sep. 30, 2015		Sep. 30, 2014	Mar. 31, 2015
Consideration
Net cash paid for acquisitions		$ 98,144		$ 29,834
Recognized amounts of identifiable assets acquired and liabilities assumed
Goodwill		1,361,031			$ 1,313,644
Series of Individually Immaterial Business Acquisitions [Member]
Consideration
Net cash paid for acquisitions		98,144	[1]	30,000
Recognized amounts of identifiable assets acquired and liabilities assumed
Current assets, net		10,139
Plant and equipment		24,275
Other intangible assets		35,154
Current liabilities		(12,014)
Non-current liabilities		(4,947)
Total identifiable net assets		52,607
Goodwill		45,537
Recognized amounts of identifiable assets acquired, goodwill, and liabilities assumed, net		98,144
Distribution Business Segment [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed
Goodwill		1,142,200			1,116,569
Distribution Business Segment [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Consideration
Net cash paid for acquisitions		53,227	[1]	$ 30,000
Recognized amounts of identifiable assets acquired and liabilities assumed
Current assets, net		7,957
Plant and equipment		11,035
Other intangible assets		21,585
Current liabilities		(7,732)
Non-current liabilities		(3,350)
Total identifiable net assets		29,495
Goodwill		23,732
Recognized amounts of identifiable assets acquired, goodwill, and liabilities assumed, net		53,227
All Other Operations Business Segment [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed
Goodwill		218,831			$ 197,075
All Other Operations Business Segment [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Consideration
Net cash paid for acquisitions	[1]	44,917
Recognized amounts of identifiable assets acquired and liabilities assumed
Current assets, net		2,182
Plant and equipment		13,240
Other intangible assets		13,569
Current liabilities		(4,282)
Non-current liabilities		(1,597)
Total identifiable net assets		23,112
Goodwill		21,805
Recognized amounts of identifiable assets acquired, goodwill, and liabilities assumed, net		$ 44,917

[1] Includes cash paid, net of cash acquired, for current year acquisitions as well as payments for the settlement of holdback liabilities associated with prior year acquisitions.