CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
CONDENSED CONSOLIDATED STATEMENTS OF INCOME
Revenue		$ 123,825	$ 117,618	$ 226,482	$ 211,251
Expenses:
Cost of revenue	[1]	43,214	33,602	85,137	65,453
Sales and marketing	[1]	6,116	2,377	12,675	4,227
Research and development	[1]	7,711	5,504	13,643	10,915
General and administrative	[1]	31,461	25,327	68,013	49,585
Depreciation and amortization		8,496	4,812	16,890	9,727
Total operating expenses		96,998	71,622	196,358	139,907
Income from operations		26,827	45,996	30,124	71,344
Other income and (expenses):
Realized losses on short-term investments		(1)		(5)
Gain on disposal of equipment				534
Interest income		1,532	615	2,974	623
Interest expense		(1,245)	(1,105)	(2,504)	(2,208)
Income before taxes		27,113	45,506	31,123	69,759
Provision for income taxes		10,862	19,370	12,507	29,864
Net income		16,251	26,136	18,616	39,895
Net income attributable to common stockholders, basic and diluted		$ 16,179	$ 26,131	$ 18,537	$ 39,891
Net income per share attributable to common stockholders, basic and diluted:
Basic net income per share (in dollars per share)		$ 0.11	$ 0.18	$ 0.12	$ 0.28
Diluted net income per share (in dollars per share)		$ 0.11	$ 0.17	$ 0.12	$ 0.27
Weighted average shares of common stock outstanding:
Basic (in shares)		151,712	147,648	151,497	141,524
Diluted (in shares)		152,706	151,299	152,548	145,149

[1] Includes stock-based compensation expense as follows: Three months ended June 30, 2016: Cost of revenue 121; Sales and marketing 152; Research and development 499; General and administrative 1,364; Total stock-based compensation expense 2,136. Three months ended June 30, 2015: Cost of revenue 29; Sales and marketing 41; Research and development 298; General and administrative 1,554; Total stock-based compensation expense 1,922. Six months ended June 30, 2016: Cost of revenue 240; Sales and marketing 306; Research and development 741; General and administrative 2,941; Total stock-based compensation expense 4.228. Six months ended June 30, 2015: Cost of revenue 57; Sales and marketing 56; Research and development 660; General and administrative 2,921; Total stock-based compensation expense 3,694.