Exhibit 12.1

Ratio of Earnings to Fixed Charges

	Year Ended December 31,										Three Months Ended March 31,
	2012		2013		2014		2015		2016		2016		2017
Fixed Charges:
Interest expense	$	14,251	$	15,341	$	17,574	$	16,888	$	42,561	$	4,870	$	17,712
Plus: estimated interest component of rent expense		3,785		5,372		5,891		5,921		8,272		2,068		2,792
Capitalized interest		2,285		4,950		4,234		3,441		8,067		3,296		7,611
Total Fixed Charges:	$	20,321	$	25,664	$	27,699	$	26,250	$	58,900	$	10,235	$	28,114
Earnings:
Income from continuing operations before income taxes	$	377,358	$	421,087	$	507,855	$	585,368	$	412,837	$	137,465	$	99,465
Plus: Fixed charges		20,321		25,664		27,699		26,250		58,900		10,235		28,114
Less: capitalized interest		2,285		4,950		4,234		3,441		8,067		3,296		7,611
Total Earnings:	$	395,394	$	441,800	$	531,320	$	608,176	$	463,670	$	144,403	$	119,968
Ratio of earnings to fixed charges		19.46		17.22		19.18		23.17		7.87		14.11		4.27