Debt Interest Expense and Other Debt Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Interest expense, debt	$ 53,254	$ 38,180	$ 37,611
Less capitalized interest	702	762	1,510
Net interest expense	52,552	37,418	36,101
Cash paid for interest	38,530	35,938	39,414
6.0% Senior Notes [Member]
Debt Instrument [Line Items]
Interest expense, debt	10,811	0	0
6.5% Senior Notes [Member]
Debt Instrument [Line Items]
Interest expense, debt	19,507	19,507	19,446
8.25% Senior Notes [Member]
Debt Instrument [Line Items]
Interest expense, debt	0	0	2,544
Amortization discount and deferred debt issuance costs [Member]
Debt Instrument [Line Items]
Interest expense, debt	3,246	1,928	1,821
Commitment Fees [Member]
Debt Instrument [Line Items]
Interest expense, debt	2,069	638	450
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest expense, debt	$ 17,621	$ 16,107	$ 13,350