Stock-based Compensation (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended					6 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2014	Sep. 30, 2014	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred tax assets (noncurrent)	$ 289,484	$ 289,021						$ 289,021
Total assets	4,198,573	3,893,979						3,893,979
Additional paid-in-capital	2,812,573	2,465,008						2,465,008
Retained earnings	292,665	216,644						216,644
Total stockholders' equity	2,971,430	2,564,477						2,564,477
Total liabilities and stockholders' equity	4,198,573	3,893,979						3,893,979
Selling, general, and administrative	158,991	175,307	144,003	96,730	103,227	199,957	343,960	519,267
Total operating expenses	586,059	586,526	537,324	437,610	434,178	871,788	1,409,112	1,995,638
Income from operations	283,553	215,803	188,464	228,090	191,562	419,652	608,116	823,919
Income before income taxes	276,523	189,723	181,823	208,803	180,886	389,689	571,512	761,235
Income tax expense	200,502	99,628	98,448	112,452	112,581	225,033	323,481	423,109
Income tax expense					112,581
Net Income (Loss) Attributable to Parent	76,021	90,095	83,375	96,351	68,305	164,656	248,031	338,126
Net income per share - basic	$ 0.74	$ 0.89	$ 0.83	$ 0.96	$ 0.69	$ 1.65	$ 2.47	$ 3.36
Net income per share - diluted	$ 0.66	$ 0.78	$ 0.73	$ 0.85	$ 0.61	$ 1.46	$ 2.19	$ 2.98
Non-cash compensation expense	103,759				75,785
Deferred taxes					(5,761)
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities	(163,523)				(14,778)
Previously Reported
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred tax assets (noncurrent)		266,869						266,869
Total assets		3,871,827						3,871,827
Additional paid-in-capital		2,404,118						2,404,118
Retained earnings		255,382						255,382
Total stockholders' equity		2,542,325						2,542,325
Total liabilities and stockholders' equity		3,871,827						3,871,827
Selling, general, and administrative		143,743	149,748	102,414	108,850	211,264	361,012	504,755
Total operating expenses		554,962	543,069	443,294	439,801	883,095	1,426,164	1,981,126
Income from operations		247,367	182,719	222,406	185,939	408,345	591,064	838,431
Income before income taxes		221,287	176,078	203,119	175,263	378,382	554,460	775,747
Income tax expense		111,111	96,358	110,384		220,204	316,562	427,673
Income tax expense					109,820
Net Income (Loss) Attributable to Parent		110,176	79,720	92,735	65,443	158,178	237,898	348,074
Net income per share - basic		$ 1.09	$ 0.79	$ 0.92	$ 0.66	$ 1.58	$ 2.37	$ 3.46
Net income per share - diluted		$ 0.96	$ 0.70	$ 0.82	$ 0.58	$ 1.40	$ 2.10	$ 3.07
Deferred taxes					(8,522)
Revision Adjustment
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred tax assets (noncurrent)		22,152						22,152
Total assets		22,152						22,152
Additional paid-in-capital		60,890						60,890
Retained earnings		(38,738)						(38,738)
Total stockholders' equity		22,152						22,152
Total liabilities and stockholders' equity		22,152						22,152
Selling, general, and administrative		31,564	(5,745)	(5,684)	(5,623)	(11,307)	(17,052)	14,512
Total operating expenses		31,564	(5,745)	(5,684)	(5,623)	(11,307)	(17,052)	14,512
Income from operations		(31,564)	5,745	5,684	5,623	11,307	17,052	(14,512)
Income before income taxes		(31,564)	5,745	5,684	5,623	11,307	17,052	(14,512)
Income tax expense		(11,483)	2,090	2,068		4,829	6,919	(4,564)
Income tax expense					2,761
Net Income (Loss) Attributable to Parent		(20,081)	3,655	3,616	2,862	6,478	10,133	(9,948)
Net income per share - basic		$ (0.20)	$ 0.04	$ 0.04	$ 0.03	$ 0.07	$ 0.10	$ (0.10)
Net income per share - diluted		$ (0.18)	$ 0.03	$ 0.03	$ 0.03	$ 0.06	$ 0.09	$ (0.09)
Deferred taxes					$ 2,761