Condensed Consolidated Statement Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 73,300	$ 85,519	$ 156,697	$ 158,350
Other comprehensive gains (losses), net of tax:
Unrealized holding gain (loss)	(580)	18	(1,324)	(48)
Loss reclassified to net income	539	436	921	874
Total other comprehensive gain (loss)	(41)	454	(403)	826
Comprehensive income	$ 73,259	$ 85,973	$ 156,294	$ 159,176