Acquisitions and Dispositions - ETG - Additional Information (Details) - USD ($) |
3 Months Ended | 7 Months Ended | 12 Months Ended | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
May 15, 2014 |
Dec. 31, 2016 |
Sep. 30, 2016 |
Jun. 30, 2016 |
Mar. 31, 2016 |
Dec. 31, 2015 |
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
Business Acquisition [Line Items] | |||||||||||||
Revenue included in consolidated statements of operations | $ 309,879,000 | $ 275,659,000 | $ 261,994,000 | $ 255,658,000 | $ 252,262,000 | $ 223,031,000 | $ 219,349,000 | $ 201,735,000 | $ 1,103,190,000 | $ 896,377,000 | $ 631,311,000 | ||
Operating income (loss) | $ 92,475,000 | $ 72,897,000 | $ 64,007,000 | $ 57,929,000 | $ 67,346,000 | $ 48,315,000 | $ 52,542,000 | $ 37,904,000 | $ 287,308,000 | $ 206,107,000 | 173,237,000 | ||
ETG [Member] | |||||||||||||
Business Acquisition [Line Items] | |||||||||||||
Acquisition date | May 15, 2014 | ||||||||||||
Purchase price of entities acquired | $ 7,200,000 | ||||||||||||
Acquisition related costs | $ 0 | ||||||||||||
Revenue included in consolidated statements of operations | $ 3,000,000 | ||||||||||||
Operating income (loss) | $ (200,000) |