Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
REVENUE	$ 574,393	$ 582,397	$ 1,146,935	$ 1,153,176
COST OF SERVICES	245,341	249,426	487,783	490,438
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	226,450	209,870	448,327	430,713
OPERATING INCOME	102,602	123,101	210,825	232,025
OTHER INCOME (EXPENSE):
Interest expense, net of interest income of $224, $20, $253 and $290	(36,231)	(37,712)	(71,423)	(76,195)
Accelerated amortization of deferred financing costs	0	(35,235)	(24)	(35,235)
Other, net	1,045	1,214	3,715	174
Other expense	(35,186)	(71,733)	(67,732)	(111,256)
INCOME BEFORE INCOME TAX EXPENSE	67,416	51,368	143,093	120,769
INCOME TAX EXPENSE	22,652	18,389	44,233	43,235
NET INCOME	$ 44,764	$ 32,979	$ 98,860	$ 77,534
EARNINGS PER COMMON SHARE—BASIC	$ 0.54	$ 0.40	$ 1.18	$ 0.94
EARNINGS PER COMMON SHARE—DILUTED	$ 0.52	$ 0.39	$ 1.16	$ 0.92
WEIGHTED AVERAGE NUMBER OF SHARES OUTSTANDING:
Basic Common	83,556	82,598	83,459	82,874
Diluted Common	85,527	84,281	85,369	84,425
DIVIDENDS DECLARED:
Dividends declared per share	$ 0	$ 0.225	$ 0.225	$ 0.45