Stock Options and Stock-Based Compensation (Details 1) (USD $)	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Stock compensation expense for time based options and performance based options
Cost of revenues	$ 81,425,000	$ 76,764,000
General and administrative	12,174,000	12,294,000
Total cost of stock-based compensation included in income before income tax provision	11,007,000	13,249,000
Amount of income tax benefit recognized	(4,411,000)	(5,051,000)
Effect on diluted net income per share	$ 0.58	$ 0.70
Time Based Options [Member] | Performance Shares [Member]
Stock compensation expense for time based options and performance based options
Cost of revenues	113,000	126,000
General and administrative	185,000	532,000
Total cost of stock-based compensation included in income before income tax provision	298,000	658,000
Amount of income tax benefit recognized	(119,000)	(256,000)
Amount charged against net income	$ 179,000	$ 402,000
Effect on diluted net income per share	$ (0.02)	$ (0.03)