Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Mar. 31, 2012
Intangible Assets (Excluding Goodwill) [Line Items]
Definite-lived intangible assets, gross carrying amount	$ 173,661	$ 173,735
Definite-lived intangible assets, accumulated amortization	78,319	74,933
Definite-llved intangible assets, net carrying amount	95,342	98,802
Total intangible assets, gross carrying amount	209,653	209,727
Total intangible assets, accumulated amortization	86,572	83,186
Total intangible assets, net carrying amount	123,081	126,541	[1]
Non-compete agreements [Member]
Intangible Assets (Excluding Goodwill) [Line Items]
Definite-lived intangible assets, gross carrying amount	12,154	12,228
Definite-lived intangible assets, accumulated amortization	10,311	10,194
Definite-llved intangible assets, net carrying amount	1,843	2,034
Customer relationships [Member]
Intangible Assets (Excluding Goodwill) [Line Items]
Definite-lived intangible assets, gross carrying amount	140,669	140,669
Definite-lived intangible assets, accumulated amortization	50,296	47,226
Definite-llved intangible assets, net carrying amount	90,373	93,443
Total intangible assets, net carrying amount	90,373	93,443
Acquired backlog [Member]
Intangible Assets (Excluding Goodwill) [Line Items]
Definite-lived intangible assets, gross carrying amount	20,838	20,838
Definite-lived intangible assets, accumulated amortization	17,712	17,513
Definite-llved intangible assets, net carrying amount	3,126	3,325
Trademarks [Member]
Intangible Assets (Excluding Goodwill) [Line Items]
Indefinite-lived intangible assets, gross carrying amount	35,992	35,992
Indefinite-lived intangible assets, accumulated amortization	8,253	8,253
Indefinite-lived intangible assets, net carrying amount	27,739	27,739
Total intangible assets, net carrying amount	$ 27,739	$ 27,739

[1] Derived from audited financial statements