Long-Term Debt (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended				0 Months Ended			9 Months Ended				9 Months Ended		0 Months Ended		0 Months Ended	6 Months Ended			0 Months Ended			6 Months Ended	0 Months Ended	6 Months Ended	0 Months Ended				6 Months Ended	0 Months Ended	6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 5.625% Senior Unsecured Notes due 2020 [Member] Senior Notes [Member]	Nov. 20, 2012 5.625% Senior Unsecured Notes due 2020 [Member] Senior Notes [Member]	Jul. 16, 2014 5.625% Senior Unsecured Notes due 2022 [Member] Senior Notes [Member]	Sep. 30, 2014 5.625% Senior Unsecured Notes due 2022 [Member] Senior Notes [Member]	Jul. 16, 2014 5.625% Senior Unsecured Notes due 2022 [Member] Senior Notes [Member]	Sep. 30, 2014 8.04% Senior Secured Notes due 2020 [Member] Senior Notes [Member]	Nov. 07, 2012 8.04% Senior Secured Notes due 2020 [Member] Senior Notes [Member]	Nov. 06, 2012 8.04% Senior Secured Notes due 2020 [Member] Senior Notes [Member]	May 28, 2010 8.04% Senior Secured Notes due 2020 [Member] Senior Notes [Member]	Sep. 30, 2014 Period Prior to November 30, 2015 [Member] 5.625% Senior Unsecured Notes due 2020 [Member] Senior Notes [Member]	Sep. 30, 2014 Period Prior to July 15, 2017 [Member] 5.625% Senior Unsecured Notes due 2022 [Member] Senior Notes [Member]	Jul. 16, 2014 Senior Secured Credit Facility - Term Loan [Member]	Jul. 16, 2014 Senior Secured Credit Facility - Term Loan [Member]	Jul. 16, 2014 Revolving Credit Facility [Member]	Jul. 15, 2014 Revolving Credit Facility [Member]	Jul. 16, 2014 Revolving Credit Facility [Member]	Jul. 16, 2014 Senior Secured Credit Facility [Member]	Jul. 16, 2014 Base Rate [Member] Senior Secured Credit Facility - Term Loan [Member] Maximum [Member]	Jul. 16, 2014 Base Rate [Member] Senior Secured Credit Facility - Term Loan [Member] Minimum [Member]	Jul. 16, 2014 Base Rate [Member] Revolving Credit Facility [Member] Maximum [Member]	Jul. 15, 2014 Base Rate [Member] Revolving Credit Facility [Member] Maximum [Member]	Jul. 16, 2014 Base Rate [Member] Revolving Credit Facility [Member] Minimum [Member]	Jul. 15, 2014 Base Rate [Member] Revolving Credit Facility [Member] Minimum [Member]	Jul. 16, 2014 LIBOR [Member] Senior Secured Credit Facility - Term Loan [Member]	Jul. 16, 2014 LIBOR [Member] Senior Secured Credit Facility - Term Loan [Member] Maximum [Member]	Jul. 16, 2014 LIBOR [Member] Senior Secured Credit Facility - Term Loan [Member] Minimum [Member]	Jul. 16, 2014 LIBOR [Member] Revolving Credit Facility [Member] Maximum [Member]	Jul. 15, 2014 LIBOR [Member] Revolving Credit Facility [Member] Maximum [Member]	Jul. 16, 2014 LIBOR [Member] Revolving Credit Facility [Member] Minimum [Member]	Jul. 15, 2014 LIBOR [Member] Revolving Credit Facility [Member] Minimum [Member]
Term Loan and Credit Facility
Borrowing capacity of new revolving credit agreement																	$ 870,000,000.0		$ 475,000,000.0	$ 300,000,000.0
Basis spread																						2.00%	1.75%	2.00%	1.00%	1.75%	0.25%		3.00%	2.75%	3.00%	2.00%	2.75%	1.25%
Floor rate																												0.75%
Current variable rate																												3.75%
Quarterly principal payment as a percent of face amount																0.25%
Annual principal payment																	8,700,000
Unused capacity commitment fee, percentage																		0.375%
Quarterly installments as a percent of initial principal amount of term loan																		0.25%
Maximum increase in borrowing capacity																					300,000,000.0
Debt extinguishment costs	(16,887,000)	0	(16,887,000)	0															(4,500,000)
Senior Unsecured Debt
Face amount						250,000,000.0			1,100,000,000.0				75,000,000.0
Interest rate						5.625%			5.625%		8.04%	6.04%
Redeemable principal percentage					35.00%			35.00%
Redemption price as percent of the principal amount														105.625%	105.625%
Debt registration rights agreement, filing period maximum							270 days
Debt registration rights agreement, registration effectiveness penalty maximum, percentage							1.00%
Senior Secured Debt
Face amount						250,000,000.0			1,100,000,000.0				75,000,000.0
Interest rate						5.625%			5.625%		8.04%	6.04%
Early termination fee										$ 12,300,000