CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings		Accumulated Other Comprehensive Income (Loss)		Non- controlling Interest
Balance at beginning of period (shares) at Dec. 31, 2016		90,586,741
Balance at beginning of period at Dec. 31, 2016	$ 610,556	$ 906	$ 653,629	$ 45,654		$ (89,633)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (shares)		326,823
Issuance of common stock	(880)	$ 3	(883)
Share-based compensation expense	3,975		3,975
Net income (loss)	7,888			7,888
Dividends	(16,604)			(16,604)
Other comprehensive income:
Pension and other postretirement benefit liability adjustment, net of tax	3,276					3,276
Balance at end of period (shares) at Jun. 30, 2017		90,913,564.000
Balance at end of period at Jun. 30, 2017	$ 608,211	$ 909	656,721	36,938		(86,357)
Balance at beginning of period (shares) at Dec. 31, 2017	91,123,759	91,123,759
Balance at beginning of period at Dec. 31, 2017	$ 655,947	$ 911	659,227	74,219		(78,410)		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (shares)		244,770
Issuance of common stock	(33)	$ 3	(36)
Share-based compensation expense	3,692		3,692
Reclassification of stranded tax effects related to the Tax Act	16,847			16,847	[1]	(16,847)	[1]
Net income (loss)	(40,359)			(40,359)
Fair value of non-controlling interest acquired	11,752							11,752
Dividends	(16,764)			(16,764)
Other comprehensive income:
Pension and other postretirement benefit liability adjustment, net of tax	$ 3,226					3,226
Balance at end of period (shares) at Jun. 30, 2018	91,368,529	91,368,529
Balance at end of period at Jun. 30, 2018	$ 617,461	$ 914	$ 662,883	$ 33,943		$ (92,031)		$ 11,752

[1] Refer to Note 1 - Recently Adopted Accounting Pronouncements within our Notes to unaudited Condensed Consolidated Financial Statements for additional details on the adoption of ASU No. 2018-02 during the first quarter of 2018.