CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 61,364	$ 62,882	$ 62,567
Adjustments to reconcile net income to net cash provided by operating activities-
Depreciation	13,380	13,616	14,776
Amortization	29,501	27,626	29,281
Amortization of original issue discount	2,790	4,866	6,246
Asset impairment	3,135		1,685
(Gain) loss on short-term investments and other	(184)	(83)	177
Loss on repurchase of convertible notes		8,651
Gain on disposition of business operations		(6,611)	(3,733)
Deferred income taxes	7,112	(2,811)	(16,106)
Excess tax benefit of stock-based compensation awards		(4,729)	(2,185)
Stock-based compensation	21,049	22,715	21,130
Changes in operating assets and liabilities:
Trade accounts receivable, net	(6,421)	(23,243)	1,831
Other current and non-current assets	2,875	255	(5,387)
Income taxes payable/receivable	(2,729)	(14,167)	8,953
Trade accounts payable and accrued liabilities	(4,377)	(5,738)	13,916
Deferred revenue	(300)	957	3,808
Net cash provided by operating activities	127,195	84,186	136,959
Cash flows from investing activities:
Purchases of property and equipment	(28,942)	(14,263)	(18,845)
Purchases of short-term investments	(182,247)	(196,967)	(181,553)
Proceeds from sale/maturity of short-term investments	193,465	157,825	192,994
Acquisition of and investments in business, net of cash acquired			(1,300)
Acquisition of and investments in client contracts	(12,180)	(7,587)	(8,018)
Proceeds from the disposition of business operations		8,850
Net cash used in investing activities	(29,904)	(52,142)	(16,722)
Cash flows from financing activities:
Proceeds from issuance of common stock	1,776	1,547	1,547
Payment of cash dividends	(26,850)	(24,110)	(22,238)
Repurchase of common stock	(30,649)	(25,196)	(65,027)
Payments on acquired asset financing			(829)
Proceeds from long-term debt		230,000	150,000
Payments on long-term debt	(15,000)	(7,500)	(127,500)
Repurchase of convertible notes		(215,676)
Settlement of convertible notes	(34,771)
Payments of deferred financing costs		(6,744)	(2,742)
Excess tax benefit of stock-based compensation awards		4,729	2,185
Net cash used in financing activities	(105,494)	(42,950)	(64,604)
Effect of exchange rate fluctuations on cash	4,095	4,626	(4,714)
Net increase (decrease) in cash and cash equivalents	(4,108)	(6,280)	50,919
Cash and cash equivalents, beginning of period	126,351	132,631	81,712
Cash and cash equivalents, end of period	122,243	126,351	132,631
Cash paid during the period for-
Interest	14,729	12,191	8,380
Income taxes	$ 22,144	$ 53,020	$ 41,860