Goodwill and Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Components of Intangible Assets
Goodwill (Not subject to amortization)	$ 1,914,827	$ 1,914,808	$ 692,166
Other intangible assets:
Customer relationships and noncompete agreements	505,367	505,367	77,904
Trademarks and tradenames (not subject to amortization)	91,100	91,100	0
Gross carrying amount	596,467	596,467	77,904
Accumulated amortization	(70,314)	(60,471)	(37,897)
Intangible assets, net	$ 526,153	$ 535,996	$ 40,007