Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]



	Quoted Prices in Active Markets for Identical Instruments (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Marketable securities	$	15,378	$	—	$	—	$	15,378

Valuation of senior notes



	December 31, 2014				December 31, 2013
(in thousands)	Carrying Amount		Estimated Fair Value		Carrying Amount		Estimated Fair Value
4.875% Senior Notes due 2021	$	497,876	$	566,700	$	497,525	$	524,434
4.625% Senior Notes due 2021	299,650		337,222		299,598		310,141
3.800% Senior Notes due 2022	299,109		310,749		299,011		290,453
3.850% Senior Notes due 2023	299,980		311,656		$	299,976	$	289,362

- Definition

Tabular disclosure of liabilities, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, by class that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3). Where the quoted price in an active market for the identical liability is not available, the Level 1 input is the quoted price of an identical liability when traded as an asset.

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