Goodwill (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
Sep. 30, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Goodwill
Goodwill at the beginning of the period	$ 1,107,006us-gaap_Goodwill	$ 555,220us-gaap_Goodwill	$ 167,245us-gaap_Goodwill	$ 8,568us-gaap_Goodwill
Acquisitions	86,895us-gaap_GoodwillAcquiredDuringPeriod	551,786us-gaap_GoodwillAcquiredDuringPeriod	387,975us-gaap_GoodwillAcquiredDuringPeriod	158,677us-gaap_GoodwillAcquiredDuringPeriod
Goodwill at the end of the period	$ 1,170,490us-gaap_Goodwill	$ 1,107,006us-gaap_Goodwill	$ 555,220us-gaap_Goodwill	$ 167,245us-gaap_Goodwill

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant