Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 74,077	$ 64,057
Accounts receivable, net of allowance for doubtful accounts of $7,390 and $6,739, respectively	264,076	243,900
Contract asset	11,942
Prepaid expenses and other current assets	35,559	38,742
Prepaid income taxes		12,166
Restricted cash	543	592
Total current assets	386,197	359,457
Property, plant and equipment:
Land	2,655	2,655
Building and improvements	61,354	59,935
Equipment, furniture, and fixtures	144,825	138,747
Total property and equipment	208,834	201,337
Less: accumulated depreciation	(106,840)	(100,381)
Net property, plant and equipment	101,994	100,956
Deferred income taxes	2,041	2,324
Contract asset	22,076
Goodwill (Note 4)	3,711,181	3,707,823
Intangible and other assets, net of accumulated amortization of $1,011,145 and $953,957, respectively	1,326,095	1,368,956
Total assets	5,549,584	5,539,516
Current liabilities:
Current portion of long-term debt (Note 3)	37,338	37,863
Accounts payable	17,637	27,087
Income taxes payable	16,182	6,031
Accrued employee compensation and benefits	42,193	96,016
Interest payable	7,620	16,425
Other accrued expenses	60,875	55,637
Deferred revenue	193,024	204,601
Total current liabilities	374,869	443,660
Long-term debt, net of current portion (Note 3)	1,949,232	2,007,332
Other long-term liabilities	120,621	118,679
Deferred income taxes	288,954	283,457
Total liabilities	2,733,676	2,853,128
Commitments and contingencies (Note 9)
Stockholders’ equity (Note 6):
Preferred stock, $0.01 par value per share, 5,000,000 shares authorized; no shares issued
Common stock	2,094	2,081
Additional paid-in capital	2,057,757	2,018,106
Accumulated other comprehensive loss	(77,438)	(82,655)
Retained earnings	851,495	766,856
Stockholders' equity before treasury stock	2,833,908	2,704,388
Less: cost of common stock in treasury, 1,573,339 shares	(18,000)	(18,000)
Total stockholders’ equity	2,815,908	2,686,388
Total liabilities and stockholders’ equity	5,549,584	5,539,516
Class A Non-Voting Common Stock [Member]
Stockholders’ equity (Note 6):
Common stock