CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Revenue		$ 437,271	$ 361,540	$ 295,798
Expenses:
Cost of revenue	[1]	146,140	112,761	120,054
Sales and marketing	[1]	14,684	7,143	5,952
Research and development	[1]	22,329	23,130	21,192
General and administrative	[1]	115,029	88,565	80,638
Depreciation and amortization		22,633	19,880	15,517
Total operating expenses		320,815	251,479	243,353
Income from operations		116,456	110,061	52,445
Other income and (expenses):
Realized losses on short-term investments		(328)
Interest income		3,003	6	9
Interest expense		(4,420)	(1,336)	(79)
Income before taxes		114,711	108,731	52,375
Provision for income taxes		48,648	43,379	19,657
Net income		66,063	65,352	32,718
Net income attributable to common stockholders, basic and diluted		$ 66,014	$ 65,352	$ 32,718
Net income per share attributable to common stockholders, basic and diluted:
Basic net income per share (in dollars per share)		$ 0.45	$ 0.50	$ 0.24
Diluted net income per share (in dollars per share)		$ 0.45	$ 0.49	$ 0.24
Weighted average shares of common stock outstanding:
Basic (in shares)		145,745	130,770	135,305
Diluted (in shares)		148,275	133,289	136,375
Cash dividend declared per share (in dollars per share)				$ 0.15

[1] Includes stock-based compensation expense as follows: Year ended December 31, 2015: Cost of revenue 164; Sales and marketing 173; Research and development 1,212; General and administrative 5,866; Total stock-based compensation expense 7,415. Year ended December 31, 2014: General and administrative 2,894; Total stock-based compensation expense 2,894. Year ended December 31, 2013: General and administrative 1,842; Total stock-based compensation expense 1,842.