Stockholders' Equity (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	1 Months Ended	6 Months Ended
	Aug. 31, 2004	Sep. 30, 2012
Summary of Repurchase Program Activity
Stock repurchase program, Authorized amount	$ 200,000	$ 300,000
Total repurchases, Aggregate Price		284,128
Available for repurchase, Aggregate Price		15,872
Total repurchases, Repurchased Shares		27,273
Total repurchases, Average Price Per Share	$ 10.04	$ 10.42
Open market repurchases [Member]
Summary of Repurchase Program Activity
Total repurchases, Aggregate Price		173,611
Total repurchases, Repurchased Shares		17,284
Total repurchases, Average Price Per Share		$ 10.04
Structured stock repurchase agreements [Member]
Summary of Repurchase Program Activity
Total repurchases, Aggregate Price		$ 110,517
Total repurchases, Repurchased Shares		9,989
Total repurchases, Average Price Per Share		$ 11.06