Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
REVENUE	$ 571,407,000	$ 574,448,000	$ 1,724,583,000	$ 1,711,829,000
COST OF SERVICES	247,817,000	246,337,000	738,255,000	731,304,000
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	214,091,000	203,757,000	644,804,000	629,045,000
OPERATING INCOME	109,499,000	124,354,000	341,524,000	351,480,000
OTHER INCOME (EXPENSE):
Interest expense, net of interest income	(36,794,000)	(38,382,000)	(112,989,000)	(115,657,000)
Accelerated amortization of deferred financing costs	(1,234,000)	0	(36,469,000)	0
Other, net	445,000	(6,322,000)	619,000	(2,583,000)
Other expense	(37,583,000)	(44,704,000)	(148,839,000)	(118,240,000)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAX EXPENSE	71,916,000	79,650,000	192,685,000	233,240,000
INCOME TAX EXPENSE ATTRIBUTED TO CONTINUING OPERATIONS	24,381,000	28,931,000	67,616,000	84,664,000
INCOME FROM CONTINUING OPERATIONS	47,535,000	50,719,000	125,069,000	148,576,000
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, NET OF INCOME TAXES	0	(1,235,000)	0	30,989,000
NET INCOME	$ 47,535,000	$ 49,484,000	$ 125,069,000	$ 179,565,000
EARNINGS PER COMMON SHARE—BASIC:
Continuing Operations	$ 0.57	$ 0.61	$ 1.51	$ 1.78
Discontinued Operations	0	(0.01)	0	0.37
Total Earnings Per Common Share—Basic	0.57	0.60	1.51	2.15
EARNINGS PER COMMON SHARE—DILUTED:
Continuing Operations	0.56	0.60	1.48	1.74
Discontinued Operations	0	(0.01)	0	0.36
Total Earnings Per Common Share—Diluted	$ 0.56	$ 0.58	$ 1.48	$ 2.10
WEIGHTED AVERAGE NUMBER OF SHARES OUTSTANDING:
Basic Common	82,870	82,931	82,873	83,479
Diluted Common	84,607	84,834	84,486	85,554
DIVIDENDS DECLARED:
Dividends declared per share	$ 0.225	$ 0.225	$ 0.675	$ 0.675