Subsequent Events - Narrative (Details) $ / shares in Units, shares in Thousands				1 Months Ended	12 Months Ended			42 Months Ended
	Jan. 01, 2019	Jan. 30, 2018 USD ($) day $ / shares	Jan. 12, 2018 USD ($) underwritten_offering shares	Dec. 31, 2017 USD ($)	Dec. 31, 2018	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 11, 2017 USD ($)	Jan. 31, 2018 USD ($)	Dec. 12, 2017 USD ($)
Subsequent Event [Line Items]
Minimum interest coverage ratio				3.0				3.0
Maximum leverage ratio				3.75				3.25
GEODynamics, Inc. [Member]
Subsequent Event [Line Items]
Business acquisition, revenue reported by acquired entity						$ 166,400,000	$ 72,100,000
Business acquisition, net income reported by acquired entity						24,400,000	$ 100,000
GEODynamics, Inc. [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Payments to acquire business			$ 295,297,000
Stock issued (in shares) | shares			8,660
Consideration transferred, equity interests issued			$ 294,910,000
Consideration transferred, unsecured promissory notes			$ 25,000,000
Number of underwritten offerings | underwritten_offering			2
Unsecured Debt [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Interest rate			2.50%
Minimum [Member]
Subsequent Event [Line Items]
Unused capacity, commitment fee percentage				0.375%				0.375%
Maximum [Member]
Subsequent Event [Line Items]
Unused capacity, commitment fee percentage				0.50%				0.50%
Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity								$ 600,000,000		$ 425,000,000
Long-term line of credit				$ 0		$ 0
Revolving Credit Facility [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity		$ 350,000,000
Minimum interest coverage ratio		3
Maximum senior secured leverage ratio		2.25
Long-term line of credit									$ 97,000,000
Revolving Credit Facility [Member] | Minimum [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Unused capacity, commitment fee percentage		0.25%
Revolving Credit Facility [Member] | Maximum [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Unused capacity, commitment fee percentage		0.50%
Letter of Credit [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity		$ 50,000,000
Long-term line of credit									$ 21,200,000
(LIBOR) [Member] | Minimum [Member]
Subsequent Event [Line Items]
Basis spread on variable rate				1.75%				1.50%
(LIBOR) [Member] | Maximum [Member]
Subsequent Event [Line Items]
Basis spread on variable rate				3.50%				2.50%
(LIBOR) [Member] | Revolving Credit Facility [Member] | Minimum [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Basis spread on variable rate		1.75%
(LIBOR) [Member] | Revolving Credit Facility [Member] | Maximum [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Basis spread on variable rate		3.00%
Base Rate [Member] | Minimum [Member]
Subsequent Event [Line Items]
Basis spread on variable rate				0.75%				0.50%
Base Rate [Member] | Maximum [Member]
Subsequent Event [Line Items]
Basis spread on variable rate				2.50%				1.50%
Base Rate [Member] | Revolving Credit Facility [Member] | Minimum [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Basis spread on variable rate		0.75%
Base Rate [Member] | Revolving Credit Facility [Member] | Maximum [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Basis spread on variable rate		2.00%
1.5% Convertible Unsecured Senior Notes [Member] | Convertible Debt [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Interest rate		1.50%
Debt instrument, face amount		$ 200,000,000
Proceeds from issuance of debt		$ 194,000,000
Debt instrument, convertible, conversion ratio		0.222748
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares		$ 44.89
Percentage of stock price trigger		130.00%
Convertible threshold, trading days | day		20
Convertible threshold, consecutive trading days | day		30
Scenario, Forecast [Member] | Revolving Credit Facility [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Maximum leverage ratio	3.75				4