Debt Interest Expense and Other Debt Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Debt Instrument [Line Items]
Interest expense, debt		$ 37,611	$ 47,651	$ 47,459
Unrealized Gain (Loss) on Cash Flow Hedging Instruments		0	849	5,095
Less capitalized interest		1,510	641	277
Net interest expense		36,101	47,010	47,182
Cash paid for interest		39,414	44,655	38,476
Loss on early extinguishment of debt		7,677	0	2,979
Repayments of senior notes	185,000	156,188	0	260,235
6.25% Interest Rate [Member]
Debt Instrument [Line Items]
Stated interest rate, senior notes					6.25%
6.5% Senior Notes [Member]
Debt Instrument [Line Items]
Interest expense, debt		19,446	19,506	15,716
Stated interest rate, senior notes		6.50%
6.25% Senior Notes [Member]
Debt Instrument [Line Items]
Interest expense, debt		0	0	2,422
Stated interest rate, senior notes
8.25% Senior Notes [Member]
Debt Instrument [Line Items]
Interest expense, debt		2,544	12,380	12,380
Stated interest rate, senior notes
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Interest expense, debt		0	0	543
Amortization discount and deferred debt issuance costs [Member]
Debt Instrument [Line Items]
Interest expense, debt		1,821	2,120	1,946
Commitment Fees [Member]
Debt Instrument [Line Items]
Interest expense, debt		450	835	621
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest expense, debt		$ 13,350	$ 11,961	$ 8,736