Quarterly Financial Data (Schedule of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Data [Abstract]
Total revenues	$ 161,035	$ 189,247	$ 193,596	$ 261,721	$ 400,911	$ 393,955	$ 359,662	$ 336,756		$ 805,599	$ 1,491,284	$ 1,262,904
Segment profits	24,992	34,317	37,022	66,412	128,729	129,835	116,732	104,569		162,743	479,865	394,816
Net income (loss)	$ (55,184)	$ (105,642)	$ (48,295)	$ (32,624)	$ (18,808)	$ 9,931	$ 2,443	$ (1,907)		$ (241,745)	$ (8,341)	$ (35,929)
Basic	$ (1.37)	$ (2.63)	$ (1.20)	$ (0.81)	$ (0.46)	$ 0.24	$ 0.06	$ (0.05)		$ (5.97)	$ (0.20)	$ (0.89)
Diluted	$ (1.37)	$ (2.63)	$ (1.20)	$ (0.81)	$ (0.46)	$ 0.24	$ 0.06	$ (0.05)		$ (5.97)	$ (0.20)	$ (0.89)
Weighted average common shares outstanding, Basic	40,148,000	40,168,000	40,168,000	40,072,000	41,332,000	41,477,000	41,342,000	40,605,000		40,505,429	41,165,940	40,288,218
Weighted average common shares outstanding, Diluted	40,148,000	40,168,000	40,168,000	40,072,000	41,332,000	42,213,000	42,043,000	40,605,000		40,505,429	41,165,940	40,288,218
Goodwill impairment		$ 81,900			$ 34,700				$ 81,900	$ 81,877	$ 34,703