Condensed Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands		Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Parent [Member]	Noncontrolling Interest [Member]	Total
Balances (in shares) at Dec. 31, 2017		39,871,314
Balances at Dec. 31, 2017		$ 399	$ 160,376	$ 634	$ 783,699	$ 945,108	$ 47,697	$ 992,805
Net income		0	0	0	35,864	35,864	7,490	43,354
Other comprehensive income		$ 0	0	1,209	0	1,209	0	1,209
Purchases of common stock (in shares)	[1]	(108,199)
Purchases of common stock	[1]	$ (1)	(6,368)	0	0	(6,369)	0	(6,369)
Restricted stock units ("RSUs") vested (in shares)		299,089
Restricted stock units ("RSUs") vested		$ 3	0	0	0	3	0	3
Dividends on common stock		0	0	0	(17,242)	(17,242)	0	(17,242)
Transactions with non-controlling interests		$ 0	0	0	0	0	(10,128)	(10,128)
Employee Stock Purchase Plan ("ESPP"), amortized RSUs and other (in shares)		(10,998)
Employee Stock Purchase Plan ("ESPP"), amortized RSUs and other		$ 0	13,231	(2)	(184)	13,045	0	13,045
Issuance of Convertible Notes (in shares)		1,199,869
Issuance of Convertible Notes		$ 12	53,086			53,098	0	53,098
ESPP, amortized RSUs and other (in shares)		10,998
Effect of adopting Accounting Standards | Accounting Standards Update 2016-02 [Member]		$ 0	0	0	(15,201)	(15,201)	0	(15,201)
Issuance of common stock for Layne acquisition (in shares)		5,624,021
Issuance of common stock for Layne acquisition		$ 56	321,019	0	0	321,075	48	321,123
Premium on 8.0% Convertible Notes		$ 0	30,702	0	0	30,702	0	$ 30,702
Balances (in shares) at Sep. 30, 2018		46,897,092						46,897,092
Balances at Sep. 30, 2018		$ 469	572,046	1,841	786,936	1,361,292	45,107	$ 1,406,399
Balances (in shares) at Jun. 30, 2018		45,688,582
Balances at Jun. 30, 2018		$ 457	516,680	1,022	737,417	1,255,576	45,410	1,300,986
Net income		0	0	0	55,672	55,672	3,425	59,097
Other comprehensive income		$ 0	0	819	0	819	0	819
Purchases of common stock (in shares)	[1]	(3,767)
Purchases of common stock	[1]	$ 0	(204)	0	0	(204)	0	(204)
Restricted stock units ("RSUs") vested (in shares)		8,768
Restricted stock units ("RSUs") vested		$ 0	0	0	0	0	0	0
Dividends on common stock		0	0	0	(6,096)	(6,096)	0	(6,096)
Transactions with non-controlling interests		$ 0	0	0	0	0	(3,728)	(3,728)
Employee Stock Purchase Plan ("ESPP"), amortized RSUs and other (in shares)		(3,640)
Employee Stock Purchase Plan ("ESPP"), amortized RSUs and other		$ 0	2,484	0	(57)	2,429	0	2,429
Issuance of Convertible Notes (in shares)		1,199,869
Issuance of Convertible Notes		$ 12	53,086	0	0	53,098	0	$ 53,098
ESPP, amortized RSUs and other (in shares)		3,640
Balances (in shares) at Sep. 30, 2018		46,897,092						46,897,092
Balances at Sep. 30, 2018		$ 469	572,046	1,841	786,936	1,361,292	45,107	$ 1,406,399
Balances (in shares) at Dec. 31, 2018		46,665,889						46,665,889
Balances at Dec. 31, 2018		$ 467	564,559	(749)	787,356	1,351,633	46,001	$ 1,397,634
Net income		0	0	0	(111,922)	(111,922)	8,793	(103,129)
Other comprehensive income		$ 0	0	(2,533)	0	(2,533)	0	(2,533)
Purchases of common stock (in shares)	[1]	(189,566)
Purchases of common stock	[1]	$ (2)	(6,914)	0	0	(6,916)	0	(6,916)
Restricted stock units ("RSUs") vested (in shares)		255,948
Restricted stock units ("RSUs") vested		$ 3	0	0	0	3	0	3
Dividends on common stock		0	0	0	(18,251)	(18,251)	0	(18,251)
Transactions with non-controlling interests		$ 0	0	0	0	0	(12,234)	(12,234)
Employee Stock Purchase Plan ("ESPP"), amortized RSUs and other (in shares)		(8,992)
Employee Stock Purchase Plan ("ESPP"), amortized RSUs and other		$ 0	9,388	0	(157)	9,231	0	9,231
ESPP, amortized RSUs and other (in shares)		8,992
Effect of adopting Accounting Standards | Accounting Standards Update 2016-02 [Member]		$ 0	0	0	(539)	(539)	0	$ (539)
Balances (in shares) at Sep. 30, 2019		46,741,263						46,741,263
Balances at Sep. 30, 2019		$ 468	567,033	(3,282)	656,487	1,220,706	42,560	$ 1,263,266
Balances (in shares) at Jun. 30, 2019		46,838,199
Balances at Jun. 30, 2019		$ 468	568,264	(3,448)	642,124	1,207,408	50,160	1,257,568
Net income		0	0	0	20,488	20,488	1,425	21,913
Other comprehensive income		$ 0	0	166	0	166	0	166
Purchases of common stock (in shares)	[1]	(101,475)
Purchases of common stock	[1]	$ (1)	(2,967)	0	0	(2,968)	0	(2,968)
Restricted stock units ("RSUs") vested (in shares)		4,555
Restricted stock units ("RSUs") vested		$ 1	0	0	0	1	0	1
Dividends on common stock		0	0	0	(6,076)	(6,076)	0	(6,076)
Transactions with non-controlling interests		$ 0	0	0	0	0	(9,025)	(9,025)
Employee Stock Purchase Plan ("ESPP"), amortized RSUs and other (in shares)		(16)
Employee Stock Purchase Plan ("ESPP"), amortized RSUs and other		$ 0	1,736	0	(49)	1,687	0	$ 1,687
ESPP, amortized RSUs and other (in shares)		16
Balances (in shares) at Sep. 30, 2019		46,741,263						46,741,263
Balances at Sep. 30, 2019		$ 468	$ 567,033	$ (3,282)	$ 656,487	$ 1,220,706	$ 42,560	$ 1,263,266

[1] Represents shares purchased in connection with employee tax withholding for RSUs vested under our 2012 Equity Incentive Plan. Amounts are comprised primarily of amortized restricted stock units.