Computation of Earnings per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Basic earnings per share:
Numerator: Net income	$ 9,967	$ 10,468
Denominator:
Weighted-average common shares outstanding (in shares)	213,640,000	217,510,000
Basic earnings per share (in dollars per share)	$ 0.05	$ 0.05
Diluted earnings per share:
Numerator: Net income	$ 9,967	$ 10,468
Denominator:
Weighted-average common shares outstanding (in shares)	213,640,000	217,510,000
Dilutive effect of stock awards (in shares)	6,054,000	3,886,000
Total shares (in shares)	219,694,000	221,396,000
Diluted earnings per share (in dollars per share)	$ 0.05	$ 0.05
Anti-dilutive shares related to stock awards excluded from EPS calculation (in shares)	2,200,000	14,500,000
Performance shares not included in EPS (in shares)	5,400,000	1,400,000