CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Current Assets:
Cash and cash equivalents	$ 445,600	$ 492,824
Accounts receivable	396,653	339,558
Unbilled services	154,345	136,878
Inventory	47,947	49,270
Deferred income taxes	47,953	44,903
Income taxes receivable	261	3,642
Prepaid expenses and other current assets	219,481	167,629
Total Current Assets	1,312,240	1,234,704
Property and equipment, net	880,953	891,319
Goodwill	109,820	109,820
Other assets	38,261	52,499
Total Assets	2,341,274	2,288,342
Current Liabilities:
Accounts payable	52,742	34,430
Accrued payroll and benefits	119,889	144,681
Accrued expenses and other current liabilities	107,008	127,686
Unearned revenue	241,681	255,776
Short-term debt	325,000	320,000
Total Current Liabilities	846,320	882,573
Deferred income taxes	20,760	27,912
Other liabilities	74,167	70,665
Total Liabilities	941,247	981,150
Commitments and Contingent Liabilities
Stockholders' Equity:
Preferred Stock - Par value $1.00 per share; 10,000,000 shares authorized; no shares issued and outstanding at June 30, 2013 and December 31, 2012	0	0
Common Stock - Par value $0.01 per share; 140,000,000 shares authorized; 80,409,500 and 79,131,299 shares issued and outstanding, including those held in treasury, at June 30, 2013 and December 31, 2012, respectively	804	791
Paid-in capital	806,993	744,114
Retained earnings	1,689,786	1,600,626
Accumulated other comprehensive (loss) income	(3,579)	28,520
Treasury stock at cost (24,514,380 and 24,145,773 shares at June 30, 2013 and December 31, 2012, respectively)	(1,093,977)	(1,066,859)
Total Stockholders' Equity	1,400,027	1,307,192
Total Liabilities and Stockholders' Equity	$ 2,341,274	$ 2,288,342